Hawaii and Caribbean diving are very different. More color in the Caribbean, much more coral, also soft corals. Hawaii is more rocky substrate and a little hard coral, less color, unique fish because it's so isolated, more big animals, and on average cooler.
I've preferred my average Caribbean dives over my average Hawaiian dives. On the other hand, I've done more dives in Hawaii that are individually memorable, because there was something unique about them. Such as lots of sharks, or lots of huge turtles, lots of mantas, interesting volcanic formations, diving with whales, my husband beating off a oceanic whitetip shark with his camera...but of course not all dives are like that.
But I wouldn't travel to either from Europe for the diving, when there are so many better places to dive that you can get to for the same effort or less. Hawaii topside is a beautiful and interesting place though. It might be worth going for that, and do some diving while you're there. (IMO most Caribbean dive destinations are not all that interesting on land, except maybe Belize.)