I love the Enchantment, especially now that it has just been refurbished and even stretched. I think it's a great choice for a 4-night cruise. There should still be availability in March, April or May.
Royal Caribbean also does 4-night cruises every Monday from Miami on Majesty of the Seas, and every Monday from Port Canaveral on Sovereign of the Seas. Of those 3 ships, Enchantment is my favorite.