I used "Blue Water" one part poly on my hull, Interlux Interthane Plus (pre Perfection that I had on the shelf) 2 part poly on the deck and the boot and cove stripes were done with automotive paint (bronze, I think laquer).
The Blue Water has failed miserably while the Interthane is in great shape, as is the automotive paint.
I chose Blue Water because it was something like $50/gallon. Huge mistake. I didn't go with Perfection because it's something like $80/quart and of course, requires friggin accessories like special brushing thinners, cha-ching.
Interlux sells an alkyd enamel for $35/quart, which is $7 more than a gallon of really good alkyd enamel house paint. Other than the word "marine" I'd doubt there is much, if any, difference.
Rustoluem has enamel marine paints for about $11/quart and is sold at our local Lowes.
I'm using Behr enamel inside my boat. I did the inside of my slider and forward hatch with one part poly, Brightside, and they mildew like crazy where the house paint doesn't at all.
When I redo my hull, I'm either going to use an enamel or automotive paint. Maybe the Behr, it's looking great so far.