I have a Ruck and an Assault pack issued to me (active Army) and I have to say that for my size (6 feet 220lbs) the Ruck is extremely comfortable. The old Metal frames were horrible especially for larger guys and heavy for their purpose. The Polymer one is a bit larger in dimension and extremely light. The only problem that I've had was when i dropped my ruck after a 12 mile ruck march with 75lbs and the frame actually cracked on me. You don't have the nice CIF people to just DX your equipment when its damaged during training for free so you might want to take that into account. The assault pack is basically an over glorified jansport with a few extra bells and whistles added on but I used to carry mine everywhere before i got an Under armor gym bag. It's also very easy to "expand" upon with add on pouches and what not. Also the Assault Pack doesn't have a frame to crack on you but then again it also doesn't distribute the weight quite as nicely. I guess it all boils down to how much you're planning on lugging around and what fits you best.