As with most of my early "technical" hunting gear I started started with the better mountaineering brands; The North Face, Dana Designs, Patagonia (I know!), Outdoor Research, etc. Until technical hunting gear became mainstream there were not a lot of options. That said, I looked for packs that were big and had heavy load capabilities. They were few and typically heavy.
The main differences I see in "hunting" specific packs vs. other packs are the load ratings and versatility. Osprey makes a great pack (I grew up ~40 miles from their shop) but have found them more lightly built than more hunting specific packs. Mountaineering packs typically top out at <~60 lb load ratings and I have found them comfortable to that point, but beyond that the suspension is lacking. That said, there are a number of packs that are comfortable beyond that. In reality it depends on how much and how heavily you use a pack for hunting vs. other pursuits. My ideal packs are and most of my packs were bought for hunting and are heavily built for size, compactable (carry camp in then day hunt), and have multiple lashing possibilities. I am getting wimpy anymore and am looking at lighter packs with the same heavy carry abilities and other hunting specific features.
For what it's worth I have usually carried dry sacks in my pack, but typically for gear. For meat I have always carried a few game bags and a few contractor bags. On long trips the game bags make a great hanging meat (cooling) bag and the contractor bags have multiple uses beyond keeping a pack clean.
