Beside Aruba, where you have already been, we have been to both the St Kitts and Curacao (the Marriott, not the Renaissance) properties. Mr jtwiz liked St Kitts better, I liked Curacao better!

Maybe my perception was colored by the fact it rained every day we were in St Kitts, including one day where the water was so deep in the streets it was up around my knees while I was shopping in Basseterre!!

As mentioned by other posters, St Kitts is definitely a more laid back island. We would walk along the ocean directly from the resort and barely see another person. Very peaceful for a vacation. We used taxis to get around, although we did walk to a couple of places to eat. I would definitely take the ferry to Nevis if we go again, it sounds like a fun day out.

Curacao as an island has more than just tourism (Oil refineries, etc.) and had a much livelier downtown feeling in Willemstad. The Marriott is an expensive cab ride from the downtown, that was one negative. When we went, there were no shops close by to pick up bottled water, soda, beer, etc. That may have changed as we were there a few years ago. However, the hotel itself was lovely, service was excellent. The beach right in front was a bit rocky (although it is stunningly pretty!), but if you walk a short way to the right you could easily get right into the water.

United Airlines no longer has a direct flight to Curacao or St Kitts from Newark, so unfortunately I doubt we will be back any time soon.