I had it narrowed down to Stone Glacier and Kifaru when I was looking. Both have sturdy frames capable of 100+ lb loads. I ended up with Kifaru because SG didn't come in camo. Kifaru seemed to have a lot more accessory, bag, frame, and lid options. Everyone seemed to rave about the comfort of the Kifaru belt system. The nice thing about Kifaru is once you have a frame there are a gob of different bags to choose from.
Even though I have both a Timberline 2 and EMR2...my go to is the EMR2. It has a lot more room. If it were me and I only had 1 bag I would choose a 6,000 cu in+. You can always cinch down a large bag but if you don't have enough room you are screwed! I've used mine on 2 dall sheep, 4 mtn goat, 1 bighorn sheep, and many deer, elk, and antelope hunts. I also use it for hauling turkey decoys and turkeys!