I didn't read through all the posts but would highly recommend Kifaru! More decisions...I know! The thing I like about Kifaru is there are so many different pouch, lid, and pocket options to customize your bag. Also, there are more bag options once you have a frame. I also liked the fact that Kifaru offered several camo patterns. If you read through ratings you'll likely notice how many posters recommend Kifaru due to the comfort of their belt. Lastly it's nice having a frame that can support 100+ lb loads!
I would highly recommend a 6,000 cu in bag or larger. It's possible to cinch down a larger bag but if you don't have enough room you are screwed! I tend to bone and pack a lot of larger critters (elk and moose in particular). I also pack out lots of capes...including life sized mtn goat, sheep, bear, etc. I've spent a lot of time hunting multi=days in Alaska on sheep and goat hunts. All of these trips require a larger volume pack. I actually have a 5,000 cu in Kifaru bag that hasn't spent any time on my frame! I have no problem grabbing my large volume Kifaru bag on day hunts or scouting trips...it's that comfortable!
I've used and abused my Kifaru for years and would highly recommend taking a look at them. There are lots of videos about their bags and frames on their website. If I wouldn't have bought Kifaru I would have bought a SG but I'm super excited I went with Kifaru!