With the group that you're going, I'd suggest cancun... it's more of a party town
there are tons of bars in playa del carmen, with the most famous being Coco Bongo...
generally speaking, food is a bit better in mexico than dominican
This. LOL at Punta Cana.
The only resort I ever go to is Club Med which is more family-friendly so I can't give any resort advice. However, downtown Cancun is where it's at. Coco Bongo was my first clubbing experience and nothing since then has come close to matching it. I recall paying something ridiculous (in a good way) like $50 for entrance + open bar, including the wild shows they put on throughout the night.