Man, I like a lot of ships. I think for small ships, I like the schooner the best. If I can ever find the time to do it, I would like to make another schooner model for a big schooner (three masted with better armor, less turning, and heavier guns. It should in actuality have better top speed than the normal schooner because it is longer, but because the fast schooner is already so fast, I think it would be bad for gameplay balance). The bigger schooner would be something like a faster, lighter, more versatile alternative to a smaller frigate (aka what the game calls a "corvette"). I also think it would be cool to add a model for a small schooner (I have already started work on the model, but it may be a while before I get much done considering the fact that I'm studying aerospace engineering)
I also like smaller frigates and "corvettes". The bigger frigates are cool, but are too slow in potc for my liking. The thing I don't like about the corvettes/etc is their stupid decks. The actual ship models are pretty good, but the decks are just stupid, so I tend to stick to schooners and brigs (particularly the brigantine even though again, the deck is stupid). Of course I'll have to try out the <i>Surprise</i>. I think that personally I do like the normal frigate better than the corvette aesthetically though. I especially like to use the "normal" frigates (really too heavy to be normal) to sail right into the middle of an enemy merchant convoy and start blasting.
Eventually I'll get to the point where I will probably have a fleet consisting of a couple of ships of the line, a frigate, and either a schooner or brig to slow down/cut off the faster ships. I think I am best on a ship of the line commanding other ships. It would be even better if I could give my ai ships a course to follow too...