I bought the large ones, for both rafts (Maravia Zephyr, 15' raft). The material is all mesh but it's pretty tough. I can't really compare to the others, but from what I've seen I'm not too concerned about long term durability. The shape isn't totally round, they taper it to generally fit the shape of a raft. Obviously, its not custom so it's not perfect but it fits well enough.
Friends here have the Andy and Bax Barney bags (and love them), and that was what I originally wanted but then I found the Pacific bag and liked the idea of the huge top opening with clam shell lid rather than the zipper. Easier to get stuff in and out.
But, I think any bag is better than no bag.