Our boat was awlgriped 5 years ago, we've really been neglectful(rode hard and put away wet) it hasn't faded much and is still glossy as new. I've never seen gel coat do that in south florida without pretty constant maintenance. When I did it, I used two coats of Kelly green, then two coats of clear over that. it isn't cheap though( I was working in a boat yard at the time). If you use gel coat there is a product made by hawk eye industries called duratech, it makes gel coat so it will spray more like paint, and it does help with the porosity a little bit. I understand that Interlux makes a somewhat decent linear urethane, but I prefer awlgrip because I'm familiar with it and it has stood the test of time.
Hope this is helpful.