We own a 2 Bdrm at the Royal Palm Beach Club in St Maarten and really like the resort. I think that Dean hit the assessment head on in that it is not quite as nice as DVC, but it is very nice (especially compared to some of the other ones on St Maarten) and is in the middle of all of the restaurants on Simpson Bay. Also, the rooms at the Royal Palm have been recently renovated and the whole place has been spruced up quite a bit. We own Week 45, but we usually go during that time. We bought this resale and paid less than 1/3 of our DVC payment for this timeshare and this year will make our 6th trip, so this is our "other" travel indulgence, however, once DD gets into school, this may become our II trader...
I also agree with JudyS that St Maarten is one of the more crowded islands, but it is not quite as bad as St Thomas in that regard. One nice thing about St Maarten is that Anguilla is just a 15 minute ferry ride away and makes for great day long beach trips where you truly feel like you have gotten away from everything, and no one has nicer beaches than Shoal Bay East on Anguilla.
If you do want St Maarten, I'd look to renting or a direct trade. Avoid the Atrium or Pelican (this would be OK, but they just built a new addition that blocks the ocean view from some of the units. I wouldn't want to trade into one of those). Flamingo would be OK, but we like Royal Palm better. Don't know about Oyster Bay.
Here is the view from our unit at Royal Palm taken a couple of years ago. Note that the Palapas are done now. Also, see the big green hillside area across the bay. Those are now taken up by Pelican Marina towers and those Pelican timeshare units on the hill are the ones with no ocean view):
Pinel Island, St Martin
Front Street, Philipsburg
Plane landing at SXM. Taken at Sunset Beach Bar on Maho Beach.