It is a common misconception that UL equipment is less durable. The G4 which I use is made of 70D ripstop nylon; the same stuff that most tent floors are made out of. The point being is that if you can look after your tent, then you should be able to look after a backpack. I mean, lets face it, who goes throwing their gear on the floor anyway? I know that I "place" my stuff on the ground-- my G4 has seen two thru-hikes of the CT, as well as countless other backpacking trips and shows no signs of wear. Either-way 70D ripstop can withstand quite a bit of abrasion, but again, I won't be dragging my pack down the trail anytime soon either.

The other reason that tradional packs are heavier is not just down to the material, but due to all the exessive additions such as multiple pockets, zippers, straps, buckles, waist/shoulder padding, aircore venting-- the list continues about what crap is added to packs these days.