The Porter pack (or style rather) gets my vote for sure. I made my own Porter replica 50L out of VX21 this past spring to take for late Spring and Summer packrafting trips, and the stripped down features to a basic pack is all I can ask for. As Dave C. mentioned it makes you more of a conscience packer, (where as with an Epic you would just throw everything in a drybag and worry about how it carries after you attach it to pack, cinching straps, smacking the side getting everything to 'fit right'. I as well used to really enjoy having pockets for water, but I've realized that when I want water, I really enjoy stopping for a minute anyways. Hip belt pockets are nice for small things if you go the Porter route.
I recently purchased a 4400 porter based on their big winter sale which I'm looking forward to using for winter packrafting trips, 70L is enormous. This is the first pack I've purchased in a long time as I usually prefer my own creation. There is a ton of positive feedback on the hybrid cuben aside from some of the stitching that can tend to look stretch, but it'll definately be different from that feeling of being able to beat up xpac for my use here on the East (WV, Penn, NC, Ky, Tenn).