Best suited for tour: In my opinion - St Kitt's - specifically a tour that includes Brimstone Hill (World Heritage Site with spectacular views)
Antigua: also well suited for a tour + beach experience. Any tour should include National Historic Park (Nelson's Dockyard, Shirley Heights, Dows Hill Interpretation Centre and Blockhouse). We organized our own tour with Lawrence - who took us to the National Historic Park (about 3 hours to do all the sites), the Natural Bridge (scenic rock formation) and dropped us at a beach for a couple of hours. Then he picked us up at the agreed upon time and returned us to the ship. His website is
I HIGHLY recommend him.
St Martin: shopping and some good beaches. We liked Orient Beach
St. Thomas: shopping and some good beaches. We have been to Magen's Bay - very pretty but no snorkeling and Coki Beach - not as pretty as Magen's but it has decent snorkeling
Barbados: very scenic island. We did an island tour and enjoyed it.
Whatever you choose to do - these are a great bunch of islands.