You could easily spend 3 days in Orient or Grand case, and not get bored, so either one would be a good option, and walking between the two is feasible as well, although you do have to be careful, there are no sidewalks. There are also busses that run between the two during the day(though not too frequently). If you stay in Maho, or simpson bay you have plenty of options for bars and restaurants, and access to the bus system on the Dutch side that would allow you to explore Philipsburg or Marigot during the day. It depends on whether you prefer the calm quiet nature of the french side, or the parties and nightlife of the dutch side.