A couple of interesting anecdotes about the unusual legal status of the French and Dutch sides of Saint Martin:
1) Thieves on one side can flee to the other. It isn't far and there is no border at all other than flags on the side of the road
2) Immigration is different: some nationalities can fly into the Dutch side without a visa but not the French side. Found this out a hard way as a person I was traveling with was informed they were on the French side illegally - excursions to Antigua require a passport and constitute and international border crossing.
The Dutch side is ridiculously expensive, food wise, the French side is amazingly cheap especially vs. the Caribbean in general.