I have used the Osprey Aether 85 (2010 model) extensively all last summer which included a 130 mile hiking/packraft trip into the AK backcountry.
The Aether is a great pack up to around 70 pounds or so. However IMO the frame is a bit too flexible to be considered a true backcountry week+ long hunting pack where you will be carrying out meat and camp in the same load. What I have started doing in looking for a sturdy backcountry backpack is applying force to the top of the backpack's frame to see how easily it buckles over. I have found the harder it is to bend the frame from the top the less it will buckle under some serious weight (100 pounds).
Granted not a fool proof way to go about it and LOTS of caveats to deal with most importantly is pack fit but it helps give me an idea of what might work and what might not. For example the frame of the Badlands Sacrifice buckles much easier than the REI Flash 65 and have found that hte REI flash (only 3 pounds) carries weight better than the 4+ pound Badlands pack as well for less money too, so now the Sacrifice pack is down the road and the REI flash pack is my new day hunt pack.
The REI XT 85 takes a lot more force to make the frame bend at all and that alone told me that it may be a great canidate if it fits for a hunting pack. For a 5 pound pack I'd say if the XT 85 fits ya it'd carry the 100# loads better than the Osprey Aether 85 and possibly even the Osprey's beefier Argon 110.
There is no fool proof way to find a good pack via the internet. Sure you can glean useful information info on which pack works for what for some people, but in the end it comes down to what fits ya. If shopping at REI buy them both use them both, find what fits ya better with heavy loads and return the other one.
Hope that helps.
Here is a pic of me 35 miles from the nearest road or ATV trail last summer with the Osprey Aether 85 with about 50-55 pounds in it (again great pack for backpacking, just not my top choice given the price as a hunting pack)