Refinishing questions

Hello
I'm about to start refinishing a Discus.Searching through this and
other forums I've noticed people are leaning towards polyurethane and
away from gelcoat.Gelcoat seems to be much easier in my situation,
since I don't have a spray booth and they don't recommend sanding poly
after you've painted.I asked about PPG Concept locally and the dealer
says that acrylic urethanes shouldn't be sanded.Their top of the line
poly is called Deltron- but he couldn't say why it is better than
Concept.There's also DuPont with it's products- and they are 3-4 times
cheaper than PPG.I wonder if they really differ in quality that
much.Please advice.
Before the paint I'll have to fix one of the canopy hinges-
the rear one - it's delaminated and moves quite a bit.Pictures of the
crack are here http://picasaweb.google.com/barowicz/Canopy. How to fix
such a small detail? It seems that it takes a lot of stress and that's
why it's cracked.

Thanks,
LB