In the past, I preferred organization; kelty used to have a pack that was divided horizontally into 4 zippered pockets. Mine suffered zipper failure, and I moved on to a surplus bergen with a main compartment and 3 big outside pockets. But then I started weighing the pack itself, and moved to using single compartment big bags: if the sleeping bag weighs 2 kilos, it's odd to be putting it into a 3 kilo pack. A bigger non-constructed pack with internal organization in ditty bags seems to be the ligtest option. YMMV.