Have done plenty of researching villas and the lowlands definitely offer the best bang for the buck as far as the villas goes.
Negative is the villa is so nice you don't want to leave and the drive to Grand Case is through Sandy Ground and about 30 minutes

Two years ago we stayed in TB had was really surprised that Sandy Ground wasn't as bad as expected except for the terror on two wheels doing crazy stunts in the streets.

While the villa in Cul de Sac is lovely, I would be hesitant to rent because this area is known for having a bad seaweed problem

While we enjoy socializing, we have found staying a week in Orient more to our liking followed by our week in Maho
I think you could find a comparable villa in Orient for possibly less minus being on the beach

also you may find some villas on the Dutch side with direct beach access