St.Lucia or St. Marteen ?

I’m currently planning my 25th birthday and want to stay at an all inclusive resort. I have been looking at both St.Lucia and St. Marteen but can’t decide between the both. Some of my past favorite trips have been been the DR, Playa del Carmen and Honolulu. Ideally I’d want to go out and explore outside of the resort at least 3 times out of the 7 days I plan to be there so I am looking for a location that has cultural attractions, lively atmosphere, outdoor activities and maybe fun nightlife (but not my priority as I am not a big party girl) Please let me know your experience and what you’d recommend.