I'm new here, but I wanted to add my two cents worth to this post. I use both backpacks and duffels. My backpacks (2 - one for my wife) hold gear for 3-14 days for lightweight moving out (on foot if necessary), while the duffel is strictly a 3-7 day kit with canned goods, etc., that I can throw in the truck and go.

My back packs came from Walmart sporting goods dept. Camo with extra pockets and padded straps and waist band. Nothing to snag and they have a tightening system depending on how much you have in them. Much better quality than you'd nomally expect from Walmart. $16.99 each.

If you look around you can find quality back packs (and duffels) for a lot cheaper than many of the brand names.