Yeah, it's called a spinnaker or spindrift top depending on the sobriety of who you are asking, and it's generally for improving the water resistance of your pack, or the ability to overstuff. This bag isn't waterproof and doesn't overstuff well, so, no extra top!

Diver, it comes down to how much you're going to be carrying, how long you'll be carrying, and what weather you expect. Firstly, how much you carry with both packs is important because if overloaded the pack will never fit you correctly and the straps will slip and you will be readjusting two times for every one step you take. It's no fun and even though I wasn't overloaded, the Deuter slipped the straps way too much. Two pals thruhiked the AT with the Atmos and loved it because of all the features it had including the mesh panel on the back which kept the actual backpack from making too much contact with their back so they would stay cool in the hot hot months. If you are going a long distance, you will shed packweight and want something small and manageable, which in this case, is the Atmos. If this pack made it through the AT, did well in the hot, hot heat, and is lighter than the Deuter, I think the answer is obvious which one you should choose. I personally still haven't gotten over a 3-day hike in which I had to readjust my Deuter pack 10 times every mile. The Atmos is also tougher, that Cordura is the bomb.

Honestly they are both Very good packs i think that i would take Osprey because i have owned one and love their packs. That being said you should probably find a way to load both up and try them out. Lots of times it comes down to how they fit on you and how they feel walking around the house or the store.

Top loader access only. If you want more access points Granite Gear and Gregory are the way to go. Cheers!

This is more of a multi-day pack. The Atmos 35 35 Liter would a good overnight size.

I just purchased the Atmos 35 (L) a month or so ago. I have used it as a day/overnight pack and like the size so far. I haven't had the chance really test it out but 38L is a good size for many things if you pack right.

Anywhere between 40L and 50L should do depending on how light or heavy you pack. Can't go wrong with osprey packs.

I have been skiing 2 seasons with it. Skins and extra pair of gloves fits perfectly in the front zipper pockets. The front open pocket can fit a shovel perfectly but the material is not strong enough and my shovel's corner is piercing a hole through it- I duct taped the inside corners of the pocket and that fixes it. The hydration system has no insulation sleeves so you will have to be creative if you use a water bladders- I use bottles to prevent freezing. The mesh back is nice and keeps your back dry but you can 't really sit on to take a break. The hipbelt pockets are nice for small tool, bad for snacks- it will freeze! In general this pack doesn't carry weight very well, unless you pack light(25lbs and under). The suspension tends to transfer the weight to your shoulders more than your hips. I like it much better for backpacking than a ski pack.
I think it is still a very lightweight and high quality pack that I still like but these are just some issue that I am aware of for BC skiing.

I was thinking the same thing. I have the Atmos 65 (2009) and was thinking of using it to hike & alpine ski Mount Washington (6000 footer in the northeast). I assume I could put the skis (with boots clipped in) to asend to the base of the bowl, drop extra weight, put the ski boots on and climb the bowl. I just don't want to destroy such a nice pack with too much weight on the side. What does everyone think?

Yeah, I know it is big, but my normal daypacks probably aren't strong enough for skis and not sure I want to buy a specialty pack (yet, at least). Also would be big enough if I decided to camp on the way up.

It's probably fine, but it doesn't have ski carry and 50L is huge for a ski pack. Make very sure you need that much before you buy it.

I second what Greg said. The Atmos 50 is great for a multi-day (2-3) minimalist hiker, but if you want to carry a few more bells and whistles, I would go with the Atmos 65. I personally own the Atmos 50 and think the pack performs beautifully. I would expect the same from the Atmos 65. You can't go wrong with Osprey.

Hey Jason,

Osprey makes great packs, but for trips up to 3 nights, for a more "non-minimalist" approach, I would probably recommend a pack more in the 4000 - 4500 cu in range. If you are comparing this pack to the Atmos 65, I'd recommend the Atmos 65 due to it's size. You would probably find the packs are equally as comfortable, but the Atmos 65 has 1000 more cu in space.

I have done a lot of long weekend trips with my Gregory Baltoro as well:

http://www.backcountry.com/store/GRE0059/Gregory-Baltoro-70-Backpack-4149-4638cu-in.html

While I prefer lightweight backpacking, I use this pack when I want to pack more stuff to be comfortable (ie bigger tent, bigger sleeping pad, more clothes). The Gregory Baltoro is a little bigger, can hold more weight than the Atmos 50 and 65, and is a little heavier at 5 lbs+, but it is very comfortable and has a lot of pockets to keep well organized. It does cost $100 more than the Atmos series, however.

Let us know if you have any other questions... hope this helps!

I dont own either of these models, but from looking at both of them in person, the only real difference besides the frame and harness/hipbelt change is that they made it out of what feels like slightly less durable materials, particularly the various straps that keep everything together and compact.