Boy, packs are a real personal thing and there's a few things to consider. It depends somewhat on how much weight you are carrying and your body type. I carry about 18 pounds, excluding my pack, and before food/water. So I wind up leaving my resupply with 33 - 35 pounds including the pack. Also, I have no hips, so I need a bag with a good hip belt system and stiff support in the back so I don't wind up carrying all the weight on my shoulders. An Osprey Aether 60 works for me, although I don't like the fact that it weighs 5 pounds. The proof is that I hardly notice it on my back a few miles into my hike, and it fits my body perfectly because I don't have to shift it around and mess with the strap settings once their set.