Osprey Stratos 36 & 50 vs Kestrel 38 & 48

As some of you already know, I've been publishing about Osprey backpacks for the last 2.5 years now (find full post list at the bottom). 

I thought a post around Osprey Stratos vs Kestrel would be helpful for most of you as they're quite a bit similar. 

In short, Stratos 36 and Stratos 50 offer 1 more additional zippered pocket at the front, and a bit more ventilation than Kestrel 38 and Kestrel 48.

But their weight distribution and external gear attachment capabilities are a bit lower, and with Stratos 36, you can't install your water bottle inside side mesh pockets without taking off the pack. 

Osprey advertises both lines as backpacking backpacks (source at osprey.com for Stratos | Sirrus and Kestrel | Kyte). 

If you're looking to get a backpack suitable for backpacking and/or hiking, I'm pretty sure you can't go wrong with either of them. 

Having said that... They do have some minor differences. 

Quick Differences

• Stratos 36 & 50 come with an additional front zippered pocket (7 pockets at total + main & sleeping bag compartments) which allows making more of your frequently used items readily available. 
  • Don't confuse this pocket with the front pouch! Front pouch isn't zippered and it is also offered by the Kestrel line - unlike the front zippered pocket. 
  • They also offer a little bit more ventilation than the Kestrel's. You can say they're more for warm weather use. 

• Kestrel 38 & 48 lack this pocket, which means that the total number of exterior pockets add up to 6 (+ main & sleeping bag compartments). 1 pocket less than Stratos. 
  • But they offer superior external gear attachment capability (bungee tie-offs, loops and daisy chains). They're perfect for attaching ice tools, snow shoes, etc. This too makes the Kestrel a more suitable option for winter adventures compared to Stratos. 
  • They also perform a little bit better in terms of distributing its weight throughout your entire body to ensure a more effective carrying. 

Overview

In short, my recommendations would be as follows: 

• Kestrel 38: The most suitable option for day hiking unless you're a heavy sweater. 
• Kestrel 48: If you're like most people and incredible external gear attachment capability isn't crucial for you... or, in other words, if you'll be backpacking, say, %80+ of the time with your pack... then I'd probably recommend the Stratos 50 over the Kestrel 48. 
• Stratos 36: For heavy sweaters, this can be a superior alternative to Kestrel 38, but read on. 
• Stratos 50: The most suitable option for multi-day hiking & camping trips. 

Most of you are probably also wondering about of their differences in the suspension. 

Let's take a look at it first and then compare the Stratos 36 to Kestrel 38, and the Stratos 50 to Kestrel 48. 

AirScape vs AirSpeed

The way I see it, there's a little bit of a confusion going on about these suspension systems. 

Some of you might have read that the AirScape (belongs to Kestrel) and AirSpeed (belongs to Stratos) are focused on effective weight distribution and ventilation departments respectively. 

Now this is true. Because even Osprey themselves explain something similar in their suspension technology page (source at osprey.com).  

But... these differences aren't huge by any means. Might not even be that noticeable for most of you.

Stratos 36 vs Kestrel 38

Compared to Kestrel 38, Stratos 36 comes with less external gear attachment options. 

Now I don't really have much problems with this unless I'm going on a winter adventure so I need things like snowshoes, ice tools, trekking poles, etc. 

But one thing I don't like about Stratos 36 is that unlike all the other models in this review, it doesn't offer horizontal access to the mesh water bottle holders at each side. 

I always wish having this feature when hiking - as it allows loading and unloading on the go, without having to take off your pack. 

Stratos 36 does have its advantage, though. It's a bit more ventilated due to it's different suspension and harness system (it does inevitably sacrifice a little bit weight distribution performance in return, though). 

It also offers an additional front zippered pocket, which is lacking in Kestrel 38. 

However, this pocket is prone to getting squeezed if/when the pack is overloaded and hence bloated outwards to the front. 

It comes down to your preferences. Comfort & ventilation wise, both packs are solid and I rated them 8/10 in my Best Osprey Backpacking Backpacks post. 

Both Stratos 36 and Kestrel 38 would be suitable for day hiking and occasional overnight camping. It's difficult to go wrong with either one of them. 

If you think that you wouldn't be camping (or even if you do so it'd be with ultralight gear) and just would be day hiking with your backpack, then I'd recommend you to check out Talon 33 [read my review]. 

It's a more streamlined and less feature rich alternative to these packs, as I explained more in my Stratos vs Talon post. 

Stratos 50 vs Kestrel 48

This is easier to decide. 

Unless incredible external gear attachment capability is crucial for you (which I'd doubt), I'd recommend you the Stratos 50 over Kestrel 48. 

The front zippered pocket will come more useful as it's less likely to get squeezed due to the bloated main compartment that pushes the equipment outwards to the front. 

Unlike Stratos 36, it is possible to access the water bottle holders on the go with the Stratos 50. 

You're also more likely to wish top notch ventilation when you're hauling 48-50 liters worth of equipment when it's warm than you do so with 36-38 liters of it. 

Here's a good video review of the Stratos 50: