There are so many islands/countries and whilst there are similarities (lovely weather, beaches) they also have very different vibes. What is it you want from your Caribbean trip? Do you want an opportunity to be immersed in the culture of an island or do you want a western style gates resort? Fully English speaking or French/Spanish OK too? Built up or less developed? My very subjective thoughts below on the places I've visited.
Barbados - Caribbean first timer. Good infrastructure, easy transport, lovely beaches, outside the hurricane zone, nice hotels but a little pricier than other islands. Direct flights from several UK airports.
Dominican Republic - can often find pretty good deals. Larger country with more to explore. Spanish speaking with a different vibe to English speaking. Hotel quality can vary widely, choose one with American clientele.
Jamaica - can feel like harder work outside of the resorts with people trying to sell you stuff. Hotels try and dissuade you from leaving resorts alone due to safety (of course they'll sell you a tour though) but its a lovely country with lots to see/do. Good party scene if that's your thing. Direct flights from the UK.
Dominica - less built up, more laid back. Very green, less beaches. Feels more natural but less to do outside of nature.
St Lucia - Pretty, very pretty. Gorgeous beaches with beautiful blue sea. Relatively easy to get around. The typical Caribbean holiday thought of by the average Brit. Direct flights from the UK.
St Kitts - less built up than many of the islands but still has some lovely resorts and beaches. Mozzies got me here though. Felt more like being in the country rather than gated away in a resort. Didn't go to Nevis which I hear is beautiful.
Bonaire - small, quiet with a focus on scuba diving. Lots of Dutch tourists. Out of all is the one I probably wouldn't return to as I'm not in to scuba.
Aruba - their slogan is one happy place and I have to agree. The city it quite built up but also has nice beaches, bars and restaurants. I think BA now flies there directly. Like Bonaire and Curacao they have their own language (Papiamento) but English, Spanish and Dutch is widely spoken.
Curacao - one of my faves. Bustling city with a floating market and a floating swinging bridge. Plenty of great bars, restaurants and beaches good two. Great energy. Nice beach bar near the airport where you can practically wave to the people on the planes landing. Need to fly via Amsterdam.
St Maarten - I've only been to the Dutch speaking side (although English widely spoken). I didn't do much here apart from lie on a beach. There is a main shopping parade in the city with various branded shops, plus restaurants and beach front bars.
US Virgin Islands - I've only been to St Thomas. I remember the most brilliant blue sea I've ever seen. Whilst lots of American tourists, it still has a very chilled Caribbean vibe. Good shopping as tax free.
Grand Cayman - high end, expensive, stylish. The local supermarket sells Waitrose products....Seven mile beach is gorgeous with the calmest, warmest sea I've been in. Hotels line the beach.
Bermuda - not geographically Caribbean but politically so. Due to geography it's often overcast although warm. I found it a strange place. There's clearly a lot of money washing around as it's very expensive to stay, to eat and drink. It's very pretty but it didn't feel like a real place to me. Lots of ex pats. I probably should have explored more. Direct flights from London.
Turks and Caicos - pretty. Lovely beaches and nice hotels but small islands with not much to do.
Bahamas - I've only been to a couple of the islands. Grand Bahama felt like the USA version of Bournemouth (with much better weather)- full of American retirees. Nassau is a bit more bustling but I wouldn't rush back. Bimini is stunning. A tiny less built up island with golf carts rather than cars. Is completely a flop on the beautiful beach type of place. You can catch a ferry to Bimini from Fort Lauderdale.
Caribbean coast of Mexico - Costa Maya/Cancun. Very resort focused and high energy. But in easy reach of Tulum and the island of Cozumel which is well worth a few days stay.