I have several of Jack's round gear bags, in fact one each of his three sizes. Couple have been in use (since I am retired a lot of use) and have had zero leakage and no damage that I can see. They are all pretty old the first two ten plus years, I forgot when I got them.
I have one of his new style roll down duffle style, just have not put the use on it like the others.
Like Jack's other stuff the bags are bomber and a lifetime of use.
I also have several Watershed bags and only had one of them leak, this was one of the early models and I used it as a possibles bag in my kayaks. It cracked along the fold line. Lasted many years and I tossed it and picked up another and it has been bomber for years. Mine are all the smaller sizes not the big long ones. Several of my boating buds do use the big Watersheds instead of the Jack's style on multiday floats and have never had problems. The plus is being easy to get to the inside stuff whatever. The material especially the new ones, may well be as strong as Jack's raft material but just not to me. Maybe just me tho as I have not torn any of mine.
Bottom line I think both are worth the money, your choice!