I would recommend St-Martin (French side). You are essentially in France (nice roads, best food, no over-building). There are plenty of nice beaches. The island is rather small so make it quite nice.

Definitely St. Maarten. Beautiful. Peaceful and also quite busy! Many things to do. Beaches are great and the food is unbeatable!

RECOMMENDATIONS:

Hotels: Divi Little Bay Resort
Car Rental: Dollar/Thrifty Car Rental
Beaches: Mullet Bay, Friars Bay, Dawn Beach
Restaurants: Lees (ribs!), La Gondola (Italian), and Rare (steak)
Must do: Lottery Farm

You should definitely be aware that the island of Saint Martin / Sint Maarten is 37 square miles in all, but is divided - almost equally - between the Dutch side (Sint Maarten) and the French side - slightly larger - (Saint Martin), and the two sides are as different as chalk and cheese !

The Dutch side is heavilly over-developed, with high rises, time-share, casinos, KFC, Burger King and (if you are interested) licensed brothels ! The accepted currency is the US Dollar.

NONE of the above 'attractions' can be found on the French side of the island, where the 'official' currency is the Euro, however US Dollars are accepted everywhere.

Apart from some good restaurants located in the casino / time share / high rise area of Maho (and a few in Philipsburg and Simpson Bay) on the Dutch side, virtually all the best restaurants on the island are to be found in Grand Case on the French side, which is generally accepted to be the 'Cullinary Capital of the Caribbean'.

I can't argue with the comments of Sarah James regarding restaurants - but they are all on the Dutch side of the island, which is far more crowded and has a totally different atmosphere.

I am also very surprised that she didn't mention Orient Bay, which has without doubt the best beach here, or Pinel island, a short boat trip ($7 return) from French Cul de Sac, which is really beautiful and always has calm water.

In regard to Dollar/Thrifty Car Rental, I suggest a good look at all the posts on the subject of that company would be worthwhile - my son-in-law suffered personally, and there are plenty of alternatives from which to choose.

St Kitts, My wife and I stayed there last April and we fell in love with this beautiful and historic island. Nothing there to remind you of home accept that the populace speaks english. Many fantastic reataurants and the beaches are numerous and spectacular on the south end. The Marriott is very nice and car rental and getting around are simple. Be prepared to go back in time because it is a little backward there. We drove at night thru the Bassetere and never felt unsafe. The people were ALL very helpful.