I haven't dived the Keys, just the Palm Beach area, but here's my take: Except for the BHB, you're going to be on boats for good diving in that part of Florida, which adds significantly to the cost. On Maui, where I've done my Hawaiian diving, there are a lot of easily accessible shore diving sites, which makes your schedule easier and more flexible, and cuts the costs. Fancy lodging in either place will cost you; I don't know about Florida, but I would imagine there are cheaper motels there, and you can definitely find inexpensive condos to rent on Maui (I've had good luck with VRBO).
Hawaii is mostly hard corals, and they are not strikingly colorful. They do support a good amount of reef life, especially if you like to move slowly. We've seen several species of moray, a bunch of nudibranchs, lots of reef fish, frogfish, porcelain crabs, sea stars, and sharks, dolphins, a manta, and even a. whale. A lot of the species are endemic, so if having a "life list" of marine species interests you, you will be checking a lot of boxes in Hawaii! The boat dives will take you places you can't get to from shore, and some of them are very interesting (the Cathedrals off Lanai, or the Mala Pier at night) but unless the swell is really up, you won't have to boat dive every day.
The reefs off West Palm were beautiful. I was surprised and delighted at the amount of color - the sponges and tunicates and other photogenic critters. Goliath groupers are amazing, and we saw lemon sharks as well. You have more options for wrecks (and they have a lot of life on them). But all the diving we did was in mild to strong current, and all of it was deep enough that, had we been on single tanks, our dive times would have been a bit on the short side for me. (Anything under an hour, unless I'm getting cold, is pretty short to me.)
So, big stuff and wrecks, West Palm has it. Low current and shore diving, Maui wins. I don't think the diving is bad either place, and if you haven't been to either, it will be even more fun because everything is new.