Hard to do, as the trips were taken at different points in life. But I'll try short bites...
Barbados - see above.
Aruba - stayed at Westin on long weekend with wife. Nothing special about beach or hotel, or island.
SXM - stayed all 3 times at westin using SPG points. Great value at 12k points for $400/night rooms. Rooms large (huge bathroom), nice property on pretty beach. Nice villas just up the beach if you need a kitchen ( Not super luxurious but perfect for family of up to 5. Got upgraded every time as SPG Gold, twice to oceanfront. Renting a car is a must, as island is scenic, with great variety of beaches and activities. Beach at Radisson is very pretty, much nicer than beach at La Samanna. Kosher items increasingly available from supermarkets. Easy trip from NYC on AA or JetBlue. Classy island, no slums. You can also do day trips to St Barts and Anguilla by ferry, but saw no need personally.
DR - went only as kid, to casa de campo, and another facility. Nice scenery, plenty of flights, but poorer island. The punta cana all inclusive scene just doesnt work for kosher folks.
PR - Went twice to San Juan at Caribe Hilton, very nice property with most private beach in San Juan. Kosher was hard to find, but plenty of nice things to see, and close to airport. Cheap rent a car as I remember. Also went to Aguadilla once, which was a very nice villa property with Jet Blue access directly to airport 5 minutes away. More secluded, but a hike to the tourist attractions like the rain forest.
Cayman - went once as kid (to a villa) and more recently for long weekend with my wife at the Westin (SPG points stay). Nice Westin, not as fancy as Ritz, and seven mile beach is very pretty and large enough to find a private spot. Best off-beach snorkeling anywhere, and stingray city is fun. No need to rent a car, as supermarket is close by. Classy island.
I don't gamble, but if that is your thing, the casino action in PR seemed the most lively, with the Westin in SXM's casino more of an afterthought. Generally, non-stop flights are key for us, and I dont like to spend for overpriced resorts.