I would add another vote to EXO. I realize there are great packs from SG, and Kifaru, etc.. I went with EXO because as some of the other members mentioned, the pack is overly comfortable. I got the K3 4800, and this bag is great for a multi-day hunt, but it cinches down and can me made smaller. The EXO lid is a nice addition, along with other accessories available for it. It carries weight amazing. This last year, I hauled out I believe 4 deer in the pack, and an elk. The pack handled the weight awesome. Another reason, is the customer service of the EXO guys. If your pack has a flaw, they'll fix it, and do it quickly. As an example, the K3 was found to have a small flaw in about 1% of the K3 frames. EXO replaced everyone's frames regardless of whether they had an issue or not. They sent me one, and my other frame was just fine.
I know the SG, and Kifaru among others are awesome packs. Honestly I don't think you can go wrong with any of them. I just prefer EXO..