Hi Bocraw, welcome to CruiseReviews! The western Caribbean has some great ports, you'll probably be visiting Costa Maya, Cozumel, Roatan and Belize. The snorkeling in all of those ports is fabulous. We always bring our own equipment. I don't bring fins because I usually don't need them unless the current is strong, then I use a pair of fins from the excursion. We've sailed on both lines and have enjoyed them equally. Our last NCL ship was the Epic and it was one fabulous cruise. Our last Carnival ship was the Valor and it was equally fabulous. Each cruise line offers its own personality and you'll have a great time with either one. To me, snorkeling is the "must do" in all of the ports I've listed.
Please let us know when you've booked!