Last year I bought a couple of RIBs from the government and one had Urethane tubes made by Wing (see http://www.wing.com/polyurethane.htm
for product info and specs). In the last year I've had the opportunity to work with them by taking one set off and replacing it with a new set I also got at auction, gluing on some necessary attachments, and in repairing some small holes in the old tube set.
I found them easy to work with in regard to gluing (but no better than hypalon), but more difficult to make a good looking repair - the work I did was easy so can't comment on if they are more difficult for the more challenging jobs.
But my main observation is that they don't seem to age as well as hypalon (even though all the product info claims they do). Rather than the oxidization that is common and somewhat restorable with hypalon tubes, these turn a kind of oily color than cannot be improved (see attached photo). I've seen many active military boats with these tubes in the last year, both grey and orange, and noticed the same thing...confirmed by some of the boat operators.
For me, if I have the choice, it will be hypalon.