Enamel paint taste good for 1 million dollars jack.
Enamel paint is basicly oil hybrid, used mostly on doors windows which requires harder finish.
Mostly there are small differences only between marine use and other for all coatings. But the differences can be fundamental for the purpose - a marine coating has to withstand huge instant changes in surface temperature (think of a wave across a grey deck in high summer), continuous immersion, UV exposure and so on. While there may not be much technically different the small changes in formulation may greatly alter the time the finish will last. A urethane/enamel hybrid has greater plasticity than a pure urethane - better for flexible surfaces perhaps. Softer though, so scratches easier. I don't like urethanes, poly or otherwise - too plastic and external to the surface, particularly from my extensive use of timber over the decades. They were introduced into various markets as a cheap, low skills based instant finish - I think they don't last much longer than it takes to put them on, and can completely bugger it up if applied wrong or to inappropriate applications. Very very hard to overcoat if starting to lift or crack, often requires full strip and start again for minor damage unless you like the repair highlighted. (I do use linear polyurethanes over epoxy or fibreglass, as they are much tougher than gel coat. I would expect a minimum of ten years on a correctly prepared deck, probably twice that with a little care and maintenance.) I have a business partner and good friend who is a senior airframe technician - all types including airbus 380. He runs national airport service hangers. He makes the observation that a satin/matt finish is always used on commercial airframes as the laminar airflow is significantly slicker through the air than a high gloss, which 'grabs' the air and drags more. This is the same with performance boats. I was looking at the hull of Secret Mens Business yesterday as she streaked past us at 18 knots - yep, matt finish below the waterline.
