I have only done Eastern on Disney, but I have done many Western itineraries on another line. (Actually 2 Eastern and 5 Western). I MUCH MUCH prefer a Western itinerary. The ports on Eastern bore me. St. Maartin was okay the first time when we did an Island tour, but how many of those can you do? Our second visit there (in May), we were bored. We did a little ferry type of excursion and pretty much stayed on the boat. We got off in the French side for a minute but found the items to be too pricey, so we got a croissant and some sodas at the French bakery and sat and waited for the bus back. Nassau and St. Thomas were meh to me, no desire to go back. San Juan- we did a cool excursion, but when we got back, we attempted to walk around and found that there was nothing really nearby. Perhaps we needed to walk a little further, but we were exhausted.
On the other hand- I LOVE LOVE LOVE Cozumel. Its my favorite port. There are beaches, decent price drinks, and cheap Souvenirs. Roatan was a great port too- very pretty and just neat place. We did an Island tour with Victor Bodden. Really good tour Jamaica is a gorgeous Island, but you do have to be careful there. I felt a little uneasy in Montego Bay, I would definitely book an excursion, but Carnival at least had a hop on, hop off bus that was cool and went to the beach, Margaritaville, market area and shopping center. We were able to get some cheap souvenirs there as well. Grand Cayman- pretty. The water is so clear and shallow near where you get off the tender. If you are into Ziplining, Cave tubing, stingrays, parasailing, or snorkeling, there is plenty do in these ports. BUT, if you are like me and not really into those things, there is still plenty to do!