IMHO, the Caribbean blows away Hawaii. We've been to Maui and Kaua'i, totaling 17 nights over two separate vacations,
but will not be going back.
From the East coast it's too difficult a trip----a full, hard day going and same coming back. Caribbean is a 3.5 hr trip.
But that's not the full story.
Regarding beauty, I also rate the Caribbean far ahead of Hawaii, and comparing the user-friendly nature of the beaches,
I reach the same conclusion. Caribbean islands are drop-dead gorgeous,
nothing like it, and the water is far and away more colorful,
clear, and beautiful. The flatter beaches are whiter, softer, and just feel like they should, "like paradise should be".
Some Hawaii beaches can be rough and almost non-usable except to admire, and certainly not easy to walk and enjoy.
Snorkeling and other water activities (especially Wave Runners, aka Jet Ski boats) are more numerous
and "better" in the Caribbean, too. Caribbean sea life is teeming with exotic fishes, colors and varieties too amazing to describe,
and the coral, ship wrecks for diving, and boating options win out again.
Even the culture of "THE islands" of the Caribbean (a la Jimmy Buffett) is far more fun. Coming back from Hawaii last time,
I said to my wife, "If I hear anyone say 'Aloha' one more time I'll going to get sick".
(Nobody in the Virgin Isles says any kind of trite, redundant, touristy greeting, thank goodness.)
I've been to the Caribbean 3 times (once for a month) and have visited every US and British VI more than once.
We had a private full-day Sea Ray excursion out of St. Thomas, with Captain & mate, seeing and enjoying all of the islands,
and that day could never come close to being repeated in Hawaii. Our family still says that's the most fun day we've ever spent.
We did do a nice NaPali Coast boating excursion on Kaua'i and it was beautiful, but it was confined to the boat and the sea was not so smooth.
We actually visited many sites in Hawaii and saw as much as we could. The Caribbean still exceeds expectations, however.
Not to mention, we can go 3 times to the Caribbean for each Hawaii excursion,
everything considered, not only flights.
I do greatly appreciate the resorts we've visited in Hawaii...Maui Ocean Club and Kaua'i Beach Club---
both were top notch, beautiful, and loads of fun, but........
I do believe it's mostly an East coast-West coast thing, so I will understand the "other side" of the argument,
and I definitely get that people have different preferences, but I'll stick with the Caribbean islands all day long. Wife & children agree.
Not having remorse for visiting Hawaii, mind you---it was great to experience it.
But we like the Caribbean experience much more.
To those who haven't been, check it out, it's truly paradise. The islands below the US and British VI are also fantastic---
St. Lucia, St Maarten, etc......so the number of options are exhaustive.