I guess, when it all boils down to it, it all comes down to what you enjoying playing the most.
I don't particularly disagree with any of the 'ratings' given to the fleet ships earlier in this thread. There again, I purchased a Fleet Nova/Rhode Island a few days ago and LOVE it! She's a nimble minx and whilst doesn't hit particularly hard, can make a real nuisance of herself and cause some real problems for larger ships! FANTASTIC ship!