Here's my two cents on the hotels I have stayed at:

I would choose the island/location you want to go to more than the hotel.

JW Cancun (although not technically in the Caribbean) is the nicest. Casa Magna Cancun is right next door and is also very good. Cancun has great night life and activities.

Aruba property is nice, but wasn't as crazy about the island itself. People are super-friendly, but it's not a tropical island and very windy. I found it hard to sit on the beach and had to sit at the pool or pool bar - not that that was a big problem. Aruba has gambling, if that's a plus.

St. Thomas Marriott and Renaissance are both nice. Do a search and you will see many of the comments. Not as much to do as Cancun, but I thought St. Thomas and day-trips to St. John/British USVI were much more beautiful.