I too went with an oil-based exterior trim
paint and have been happy with the results on my boat. I wanted it glossy because, in my experience, the gloss tends to diminish over time and it reflects light well in notoriously under-lit boats. If you start with a satin finish it will be dimmer inside to begin with but, preferences vary.
Even Don Casey says you can get away with this cost-savings measure and as soule says, I've got a half gallon left over from a gallon that cost half what a quart of a marine
paint would have cost me! and the advantage to that is that, should you need to do further coats, touch-up, or repaint you're not looking at another large budget expense and therefore more likely to do it.