You've listed 4 places with good diving but that are very different, best really depends on what you like.
I've been to T&C and Curacao, both great places to dive but very different above and below. T&C has nice walls and a better chance of seeing stuff like eagle rays or sharks cruising by, though you still need some luck. Curacao is more sloping dropoffs and reefs with lots of the smaller stuff, though you'll probably see a few turtles and stingrays and may see the occasional nurse shark. Lots of shore diving in Curacao, and you can stay at a place like Habitat and have great shore diving right at the hotel. T&C is not a shore diving place. You will probably have shorter boat rides in Curacao, if you stay on Provo it's a much longer trip to the good stuff.
If you go to Curacao you will feel more like you are visiting a foreign country. In T&C (at least Provo) you may feel a bit as if you haven't left the USA. Willemstad, Curacao is interesting sightseeing and it's also interesting to tour around the island. Provo seems fairly bland to me. Both have some shopping and plenty of restaurants. Curacao has lots of small unique beaches tucked away in coves, what the hotels have for beaches varies alot. Provo is famous for Grace Bay, with a long wide stretch of beautiful sand, and most of the hotels are on it, except for a few lower priced options.