Going from top to bottom: Atom SL (soon to be called Atom Lightweight), Atom (formerly LT) and Atom Heavyweight (formerly AR). Click on image to view their side-by-side comparison on arcteryx.com.
I've got all Atoms. Including the new versions for Winter 2024 season.
Summary
It's like comparing apples to oranges.
Atom Hw is designed for stationary or low-output use at most. It's much warmer and wind resistant than Atom.
Atom, on the other hand, is for high output activities. It provides much better breathability and mobility compared to Atom Hw.
This, in my opinion, is what your decision should primarily be based on.
Links:
- https://arcteryx.com/us/en/shop/mens/atom-heavyweight-hoody
- https://arcteryx.com/us/en/shop/mens/atom-hoody
- https://arcteryx.com/us/en/shop/womens/atom-heavyweight-hoody
- https://arcteryx.com/us/en/shop/womens/atom-hoody
- Atom HW vs Atom compared side-by-side: https://arcteryx.com/us/en/compare/X000007302-heritage/X000007487-edziza
Also read:
Warmth
There's one thing that makes Atom HW unique in terms of the distribution of insulation.
It might not be a game changer but I personally really like the idea.
Performance data axis of synthetic jackets (table above) and shell jackets (this table) are different. Don't compare them.
Name Activity Temp (F/C) Breathability Weather Res. Durability Bottom line Review Pit zips? Two way zipper? Stuffs into itself? Face Fabric Fit Weight Length Alpha (aka AR) (Men's - Women's) Climbing N/A 8/10 9/10 8/10 4/10 Go-to climbing harshell. Review Yes No No N40d & N80d Most Rugged 3L Gore-Tex Pro Regular 430 g / 15.2 oz 79.5 cm / 31.25 in No Alpha SV (Men's - Women's) Climbing N/A 8/10 10/10 10/10 3/10 Strongest climbing hardshell. Review Yes No No N100d Most Rugged 3L Gore-Tex Pro Regular 510 g / 1 lb 2 oz 78 cm / 30.75 in No Beta (Men's - Women's) All Round N/A 6/10 7/10 7/10 8/10 Streamlined all-doer shell. Review No No No N30p-X 3L Gore-Tex Trim 300 g / 10.6 oz 76 cm / 30 in No Beta AR (Men's - Women's) All Round N/A 8/10 9/10 9/10 4/10 Go-to all-round harshell. Review Yes No No N40d & N80d Most Rugged 3L Gore-Tex Pro Regular 460 g / 1 lb 76 cm / 30 in No Beta AR StormHood (Men's - Women's) All Round N/A 8/10 9/10 9/10 4/10 Review Yes No No N40d & N80d Most Rugged 3L Gore-Tex Pro Regular 460 g / 1 lb 76 cm / 30 in No Beta Coat (Women's) All Round N/A 6/10 5/10 No data 5/10 No Yes No 3L Gore-Tex Regular 320 g / 11.3 oz 88 cm / 34.5 in No Beta Down Insulated (Men's) All Round 0/-18 9/10 7/10 8/10 No data Yes Yes No 2L 40D Gore-Tex Regular 760 g / 1 lb 10.8 oz 79 cm / 31 in No Beta Insulated (Men's - Women's) All Round 21/-6 9/10 7/10 8/10 No data Go-to hybrid jacket. Review Yes Yes No N40d 2L Gore-Tex Regular 680 g / 1 lb 8 oz 78.5 cm / 31 in No Beta Insulated Coat (Women's) All Round 16/-9 7/10 No data No data No data No Yes No N40d 2L Gore-Tex Regular 600 g / 1 lb 5.2 oz 86 cm / 34 in No Beta Lightweight (Men's - Women's) All Round N/A 8/10 7/10 7/10 6/10 Review Yes No No N40p 3L Gore-Tex Fitted 380 g / 13.4 oz 75 cm / 29.5 in No Beta LT (Men's - Women's) All Round N/A 7/10 7/10 8/10 6/10 Review Yes No No N40d 3L Gore-Tex Fitted 395 g / 13.9 oz 76 cm / 30 in No Gamma (aka LT) (Men's - Women's) All Round N/A 7/10 3/10 7/10 3/10 Go-to softshell. Review No No No Wee Burly Double Weave Regular 545 g / 1 lb 3.2 oz 76 cm / 30 in No Gamma MX (Men's) All Round N/A 6/10 4/10 8/10 3/10 Strongest softshell. Review No No No Fortius 2.0 Regular 555 g / 1 lb 3.6 oz 74 cm / 29.1 in No Norvan Shell (Men's) Running N/A No data No data No data No data No No No 13D 3L Gore-Tex Trim 190 g / 6.7 oz 73 cm / 28.75 in No Rush (Women's) Skiing N/A 8/10 9/10 9/10 3/10 Go-to ski jacket. Review Yes No No N80p-X & N100p-X 3L Most Rugged Gore-Tex Pro Regular 590 g / 1 lb 4.8 oz 79.5 cm / 31.25 in No Rush Insulated (Women's) Skiing 16/-9 3/10 5/10 5/10 9/10 Review No No Yes Hadron 2L Gore-Tex Infinium Regular 515 g / 1 lb 2.2 oz 79 cm / 31 in Yes Sabre (Men's) Skiing N/A 8/10 8/10 7/10 2/10 Review Yes No No N80p-X 3L Gore-Tex Regular 705 g / 1 lb 8.9 oz 79 cm / 31 in No Sentinel (Women's) Skiing N/A 8/10 7/10 7/10 2/10 Go-to ski jacket. Review Yes No No N70p 3L Gore-Tex Regular 640 g / 1 lb 6.6 oz 73.7 cm / 29 in No Sentinel Insulated (Women's) Skiing 21/-6 8/10 No data No data No data Review Yes No No N80p 2L Gore-Tex Regular 600 g / 1 lb 5.2 oz 79.8 cm / 31.5 in No Sentinel Relaxed (Women's) Skiing N/A No data No data No data No data Yes No No N80p 3L Gore-Tex Regular 655 g / 1 lb 7.1 oz ? No Sidewinder (Women's) Skiing N/A 8/10 8/10 7/10 2/10 Yes No No N80p 3L Gore-Tex Regular 570 g / 1 lb 4.1 oz ? No Solano (Men's - Women's) Around Town N/A No data No data No data No data Review No No No Gore-Tex Infinium Relaxed 355 g / 12.5 oz 72 cm / 28.3 in No Squamish (Men's - Women's) Running N/A 5/10 4/10 7/10 9/10 Go-to running jacket. Review No No Yes 30D Tyono Trim 140 g / 4.9 oz 77.5 cm / 30.5 in No Theriss Down (Women's) Skiing No data 7/10 6/10 7/10 2/10 Review Yes No No N80p 2L Gore-Tex Regular 709 g / 1 lb 9 oz 63 cm / 24.8 in No Alpha FL (Men's - Women's) Climbing N/A 7/10 No data No data 10/10 No No Yes Hadron 3L Gore-Tex Trim 209 g / 7.4 oz 76.5 cm / 30 in Yes Alpha IS (Men's) Climbing 23/-5 7/10 5/10 No data 8/10 No Yes Yes N40p-X 2L Gore-Tex Regular 610 g / 1 lb 5.5 oz 78 cm / 30.75 in Yes Alpha SL (Men's - Women's) Climbing N/A 5/10 7/10 No data 9/10 No No Yes N40p 3L Gore-Tex Trim 326 g / 11.5 oz 77.5 cm / 30.5 in Yes Beta SV (Men's - Women's) All Round N/A 8/10 10/10 10/10 3/10 Strongest all-round harshell. Review Yes No No N80p-X Most Rugged 3L Gore-Tex Pro Regular 495 g / 1 lb 1.5 oz 79 cm / 31 in Yes Gamma SL (aka lightweight) (Men's - Women's) All Round N/A 7/10 2/10 6/10 5/10 Review No No No Fortius 1.0 Trim 310 g / 10.9 oz 74 cm / 29.1 in Yes Incendia (Women's) Skiing N/A 8/10 9/10 9/10 3/10 Review Yes No No NP100d 3L Gore-Tex Trim 610 g / 1 lb 5.5 oz 79 cm / 31 in Yes Incendo (Men's) Running N/A 7/10 4/10 5/10 10/10 Review No No Yes Lumin Trim 125 g / 4.4 oz ? Yes Incendo Airshell (Men's Running N/A No data No data No data No data No No Yes ? Trim 105 g / 3.7 oz ? Yes Incendo SL (Men's) Running N/A 7/10 4/10 4/10 10/10 Review No No Yes Permair 20 & Canim Trim 80 g / 2.8 oz 73 cm / 28.75 in Yes Macai (Men's) Skiing 5/-15 7/10 7/10 6/10 1/10 Review Yes No No N40p-X 3L Gore-Tex Regular 990 g / 2 lb 2.9 oz 75 cm / 29.5 in Yes Macai Lightweight (aka LT) (Men's) Skiing 8/-13 7/10 7/10 6/10 2/10 Review Yes No No N40p-X 3L Gore-Tex Regular 855 g / 1 lb 14.2 oz ? Yes Macai Shell (Men's) Skiing N/A No data No data No data No data Review Yes No No N80p-X 3L Gore-Tex Regular 775 g / 1 lb 11.3 oz ? Yes Micon (Men's) Skiing N/A No data No data No data No data Yes No No N80p 3L Gore-Tex Regular 685 g / 1 lb 8.2 oz 83 cm / 32.5 in Yes Micon Heather Skiing N/A No data No data No data No data Yes No No NP100-d 3L Gore-Tex Regular 685 g / 1 lb 8.2 oz 83 cm / 32.5 in Yes Nodin (Men's - Women's) Running N/A 8/10 5/10 5/10 10/10 No No Yes 20D Tyono Trim 130 g / 4.6 oz 75 cm / 29.5 in Yes Norvan LT (Men's - Women's) Running N/A 5/10 5/10 8/10 6/10 No No No N13p 3L Gore-Tex Trim 190 g / 6.7 oz ? Yes Norvan SL (Men's - Women's) Running N/A 7/10 6/10 8/10 8/10 Review No No Yes Gore-Tex Infinium Trim 120 g / 4.2 oz 77 cm / 30.4 in Yes Norvan SL Ins. (Women's) Running 39/4 No data No data No data No data No No Yes Gore-Tex ShakeDry Trim 270 g / 9.5 oz 71.5 cm / 28.1 in Yes Norvan Windshell (Men's Running N/A No data No data No data No data No No Yes Permeair 20 Trim 90 g / 3.2 oz 73 cm / 28.75 in Yes Procline (Men's) Skiing N/A No data No data No data No data Yes No No N70p Gore-Tex Infinium Trim 720 g / 1 lb 9.4 oz 76 cm / 30 in Yes Ravenna (Women's) Skiing N/A 8/10 7/10 8/10 3/10 Review Yes No No N70s-4 3L Gore-Tex Trim 725 g / 1 lb 9.6 oz 69.5 cm / 27.4 in Yes Ravenna LT (Women's) Skiing N/A 6/10 6/10 6/10 5/10 Review Yes No No N70p 3L Gore-Tex Trim 540 g / 1 lb 3 oz 69 cm / 27.2 in Yes Sabre AR (Men's) Skiing N/A 7/10 8/10 7/10 7/10 Review Yes No No N70p 3L Gore-Tex Regular 700 g / 1 lb 8.7 oz 79 cm / 31 in Yes Sabre Insulated (See related products) Skiing No data 7/10 No data 6/10 No data Review Yes No No N80p 2L Gore-Tex Regular 815 g / 1 lb 12.7 oz 76 cm / 30 in Yes Sabre LT (Men's) Skiing N/A 7/10 8/10 7/10 8/10 Review Yes No No N80p 3L Gore-Tex Regular 660 g / 1 lb 7.3 oz 83 cm / 32.5 in Yes Sabre SV (Men's) Skiing N/A 10/10 10/10 10/10 1/10 Strongest ski jacket. Review Yes Yes No N100d Most Rugged 3L Gore-Tex Pro Regular 595 g / 1 lb 5 oz 85 cm / 33.5 in No Sentinel AR (Women's) Skiing N/A 7/10 8/10 7/10 7/10 Review Yes No No N70p 3L Gore-Tex Regular 590 g / 1 lb 4.8 oz 72.5 cm / 28.5 in Yes Sentinel LT (Women's) Skiing N/A 7/10 8/10 7/10 8/10 Review Yes No No N80p 3L Gore-Tex Regular 565 g / 1 lb 3.9 oz 73.5 cm / 29 in Yes Shashka Stretch (Women's) Skiing N/A No data No data No data No data Yes No No N70p Gore-Tex Infinium Trim 670 g / 1 lb 7.6 oz 71 cm / 28 in Yes Trino SL (Men's) Running N/A 8/10 5/10 7/10 6/10 Review No No No Gore-Tex Infinium Trim 340 g / 12 oz 74 cm / 29.1 in Yes Trino SL Anorak (Women's) Running N/A 8/10 7/10 8/10 7/10 Review No No No Gore-Tex Infinium Trim 290 g / 10.2 oz 65 cm / 25.5 in Yes Venda Anorak (Women's) Around Town N/A No data No data No data No data No No No Gore-Tex Relaxed 255 g / 9 oz 75.5 cm / 29.7 in Yes Zeta AR (Men's) Hiking N/A 7/10 8/10 7/10 4/10 Yes No No 3L Gore-Tex Regular 425 g / 15 oz 80 cm / 31.5 in Yes Zeta FL (Men's - Women's) Hiking N/A 4/10 6/10 4/10 6/10 No No No N20r 2L Gore-Tex Trim 221 g / 7.8 oz 76 cm / 30 in Yes Zeta LT (Men's - Women's) Hiking N/A 5/10 7/10 8/10 5/10 No No No N40P-X 3L Gore-Tex Trim 335 g / 11.8 oz 78 cm / 30.75 in Yes Zeta SL (Men's - Women's) Hiking N/A 3/10 5/10 4/10 5/10 Review No No No 2L Gore-Tex Trim 310 g / 10.9 oz 77.8 cm / 30.6 in Yes
Most Arc'teryx jackets are equipped with only one insulation density throughout the jacket. It's the same thickness everywhere.
This causes some areas to be over insulated and other areas to be under insulated. Both has their own downsides.
Forget the negative impact that over insulation has on the weight for a second. Because what we're talking about is grams in here.
The primary negative impact of over insulation can mostly be on hindering mobility and comfort. Because some areas, like underarms, do not need that much of insulation.
The primary effect of under insulation is warmth (surprising news). Some areas, like the yoke, can require more insulation. Because it prevents the heat from escaping.
That's why Arc'teryx equips some of their jackets with not one but two different insulation thicknesses. Like the Beta Insulated (Men's - Women's - read my review), Therme (Men's - read my review) and Thorium (Men's - Women's - read my review).
Atom HW is the only Arc'teryx jacket that is equipped with not one, not two, but three different insulation thickness:
- 120 g/m2 of Coreloft around the yoke, the top of the sleeve, the sides, and the back.
- 80 g/m2 of Coreloft in the bottom of the sleeves and in the zip guard.
- 60 g/m2 of Coreloft everywhere else (the front).
This customized insulation distribution makes the Atom Hw more comfortable compared to other jackets with similar warmth.
The Atom is still more comfortable than the Atom Hw, though. Because it's insulated less (60 g/m2 of Coreloft everywhere).
Source of above information:
These are pretty much the biggest differences between the two models. Atom HW is significantly warmer and less comfortable compared to the Atom.
If you're truly active inside the Atom HW, you're likely to overheat. Despite the side fleece panels.
For low output activities; like hiking, mountaineering, or resting between climbing sets; however, Atom Heavyweight would be outstanding, in addition to stationary use (no output).
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Now, although it's quite difficult to pinpoint the warmth differences between these two jackets, let me do my best and at least try to give you an idea:
Generally speaking, with only a long sleeved shirt under and without a shell on top, for an average person, during daily use (strolls, power walks, etc) and with enough wind to cause an umbrella to twist in your hand:
...without feeling uncomfortably cold, the lowest temperature to wear an Atom would be 36 deg F (2 deg C), and Atom HW around 18 deg F (-8 deg C).
With at least a moderate quality layering:
...Atom would be at 25 deg F (-4 deg C), and Atom HW at 7 deg F (-14 deg C).
With a good base layer under and a shell jacket on top:
...Atom would be at 10 deg F (-10 deg C), and Atom HW at -4 deg F (-20 deg C).
Links:
- https://arcteryx.com/us/en/shop/mens/atom-heavyweight-hoody
- https://arcteryx.com/us/en/shop/mens/atom-hoody
- https://arcteryx.com/us/en/shop/womens/atom-heavyweight-hoody
- https://arcteryx.com/us/en/shop/womens/atom-hoody
- Atom HW vs Atom compared side-by-side: https://arcteryx.com/us/en/compare/X000007302-heritage/X000007487-edziza
Breathability
Atom Hw's small armpit mesh panel.
Atom is the only line in Arc'teryx's entire insulated jacket line-up that offers mechanical ventilation.
In other words, side fleece panels.
However, how these panels are incorporated into these jackets still make them very different than one another.
Look at the side fleece panels of Atom Hw. They only takes place in the armpit area.
They're small and doesn't help that much with ventilation.
Now look at Atom's much larger panels. They span all the way from the armpits to the hem.
Atom's large side fleece panel.
They're spectacular in terms of providing breathability. This single thing gave the Atom the fame it has today.
For reference, Atom SL (soon to be called Atom Lw) has even LARGER panels than the Atom!
It's even more breathable. Check out this Proton vs Atom guide to see its images and read more about it.
Panels this large can be a mixed blessing, though. Which brings me to my next point.
Weather Resistance
Water resistances of these two are top notch. I'm 100% sure they're not going to disappoint. They're coated via DWR, too.
DWR is a coating. It's basically sprayed on to the surface of these jackets as a finish. It stands for Durable Water Repellent - which means that water will be repelled under wet conditions instead of soaking into the fabric. DWR also decreases dry time. It's a good thing these jackets are coated in DWR. But pay attention to the fact that DWR is a coating - meaning that it will wear off over time. Which is why you might want to invest in a DWR spray such as this one at arcteryx.com for after treatment. As you see, there's a strong correlation between FP x FW and temperature ratings, but not more than, say, 80%. I explained why this happens here in this post of mine.
When it comes to the wind resistance, however, it's another story. As you can guess by now, Atom Hw is off the charts in this regard too.
But when your arms are up, Atom's side fleece panels invite lots of wind and hence cold in. Even when your arms aren't up, it still does that although not equally as much.
This is something you should to consider.
Abrasion Resistance
The numbers you see in face fabrics indicate the density (in other words the thickness) of face fabric.
So, 30D Tyono face fabric of Atom Hw is stronger than 20D Tyono face fabric of Atom. It better resists against the abrasion when bouldering and backpacking.
Canberk is 5'11" and 165 pounds, with an athletic build. Size Medium fits him perfectly across almost all brands and product lines. 
Durability
You'd expect the same relationship between them in terms of durability, too. But there's a caveat here.
Larger side fleece panels of the Atom help with stretching more. This puts less stress on stitches over time, and hence can increase the life of jacket.
If you have no plans to use these jackets close to a decade, then you can simply ignore this difference.
The stretchier nature of Atom also makes it more comfortable and allows more mobility. Although I do appreciate the "too small" armpit panels of Atom Hw, they just offer less mobility.
If you need more durability, definitely check out Proton (Men's - Women's - read how it compares to the Atom) and Proton Heavyweight (Men's - Women's - read how it compares to the Atom Hw).
Pockets
Number of pockets are the same. 2 hand warmers and 1 internal zippered chest pocket in each.
Sizes of them are very similar too.
- Atom Hw:
- Hand warmers: 9.4 in (or 24 cm) x 6.7 in (or 17 cm)
- Internal zippered chest pocket: 10.6 in (or 27 cm) x 7.5 in (or 19 cm)
- Atom:
- Hand warmers: 10.6 in (or 27 cm) height x 7.1 in (or 18 cm) width
- Internal zippered chest pocket: 9.9 in (or 25 cm) height x 7.5 in (or 19 cm) width
Cuffs
Both are pretty elastic.
Left: Atom Heavyweight. Right: Atom.
Conclusion
Atom Heavyweight is a loftier, warmer, more weather resistant and durable version of the Atom. It did not have any alternatives to it for a long time. That's why everyone lost their minds when Arc'teryx shortly "discontinued" it.
Now we have the Proton Heavyweight (Men's - Women's - read how it compares to the Atom Hw), though.
The Atom, on the other hand, is best used for high output activities in general. It's light and comfortable. If climbing is what you're going to do, then I'd mostly recommend the Proton (Men's - Women's - read how it compares to the Atom) instead of this one. It's more abrasion resistant.
Both Atom HW and Atom offer mesh side panels which span all the way from the armpits to the hem. These panels are popular. They make them more breathable than all the other Arc'teryx synthetics.
Keep in mind that overheating inside the Atom HW is easier because it's very warm. That's why people say it's more breathable than the Atom HW.
Lastly, both are fantastic jackets that won't disappoint.
Links:
- https://arcteryx.com/us/en/shop/mens/atom-heavyweight-hoody
- https://arcteryx.com/us/en/shop/mens/atom-hoody
- https://arcteryx.com/us/en/shop/womens/atom-heavyweight-hoody
- https://arcteryx.com/us/en/shop/womens/atom-hoody
- Atom HW vs Atom compared side-by-side: https://arcteryx.com/us/en/compare/X000007302-heritage/X000007487-edziza
Also read:
Long ago I've had captured this on arcteryx.com. Saved it to my computer. Here's their take on both jackets.
Check out our other content on jackets:
Guide: Insulated & Shell Jackets
Start here:
Also see: