The Kuiu looks a lot like the Ortlieb 110 duffel to me, which is a great bag. I haven't found anything out there tougher than the yeti though. Downsides of Yeti are price, a little heavy, and the opening is a little narrow and can be annoying loading stuff in and out, but it is bullet proof. If you need the toughest, going to be airline traveling a lot, I'd go with Yeti. If you want something with a few more features and a bit lighter but still waterproof, Kuiu probably fits the bill, or save a few dollars and grab the Ortlieb.
Just for an example or durability, I had the Yeti 100 duffel for 5 years before baggage carriers destroyed it. That was dozens of flights and trips. I have the 50L still and it's going strong since they came out. The Ortlieb had a puncture after two flights. Either is more than enough for back of truck or even raft trips, but I think airlines today are actively trying to destroy your stuff