When determining what paint/coating system is best for your vessel, the decision will come down to three elements: time, level of finish, and budget.
Traditional one-part paint (alkyd enamel) applies right from the dispenser and evaporates quickly. It has good weatherproofing qualities, and the base can be modified for gloss, hardness, or longevity by using various additives.
The two-part polyurethanes are formed by mixing components. That mix triggers a chemical reaction that forms the cure surface. When comparing the two processes, the two-part product dries quicker and offers a higher level of finish, a shinier gloss, color retention, hardness, longevity, chemical and abrasion resistance, and overall compound integrity. Consequently, the two-part process costs more and requires more time and labor.