Royal Palm has Roxxy next door as well as a lot of evening options, but I don't care for the beach in the Kim Sha/Atrium/Royal Palm areas but the pools are fine.

Royal Islander has fewer places in the evening but is walking distance to Mullet which is a pretty good beach to spend a day. Maho beach comes and goes and the pool area at RI is pretty nice and of course it is fun to watch the jets.

I would rent a car at either but that is me, if beach is important and you don't want to travel to a beach I wouldn't stay in the Simpson Bay area.

Have fun, I still have pretty fond memories of taking our college age daughter to SXM and having some fun evenings enjoying cocktails at different bars.
Cheers,
Todd