J.C.
I've been to Cancun (business trip) and Cozumel (vacation). Although the resorts were beautiful what stands out to me most was the starving, skinny dogs that roamed the streets. (This was over a decade ago though) I have also been to Barbados, Jamaica and the Cayman Islands.
Hands down the Cayman Islands were my favorite. I loved Barbados too but it was a far trip coming from phila so I wouldn't go there again.