I'm sure this has been discussed and re-discussed. But just in case there's an updated answer.
I have a P16 that I bought super cheap. Like most older boats it needs work. This year's project is to dry out the hull and repair and repaint.
I've read up on gelcoat and I really want to avoid it. So it comes down to what kind of paint to use. I need to mention that the boat spends most of the year on dry land, and the other great percentage of time it spends on 2-4 day trips in freshwater and the occasional saltwater outing. So anti-fouling is a waste of time. I'd be willing to explore options for the very bottom that would reduce skinning that occurs when you beach, but other than that I don't think I'd need anything real hard-core.
My needs in order of priority:
Effectively waterseal
Anti-skinning something for the bottom.
Repaint (if need be) every 3-5 years is acceptable.
Strong chemical bond to fiberglass.