To the OP -- an unanswerable question without a lot of caveats.
For example, the "best place to be a scuba diver" may well depend on:
a. Employment to pay for one's recreational habit. I'm sure it will come as a shock to some people, but not all divers are independently wealthy and thus need to be employed in order to "have a life." Thus it MAY be a requirement for "the best place" that there be numerous, and lucrative, jobs available. I have not been to the Florida Keys, for example, but I'd be willing to bet there are more lucrative jobs available in the L.A. or Seattle areas than in the Keys. (And yes, I am aware of unemployment rates, but if, for example, you are a skilled software techie, there are jobs available in those two areas -- a skilled busboy, maybe not so much.)
b. How close do you want to be to your diving? If you want to be able to sit at home and say "I'd like to be in the water in 60 minutes" or "I think I'll swing by for a dive after work" then you'll probably need to be close to shore diving spots which may well leave out a lot of Florida (for example).
c. Do you care what the water temps are?
Lots and lots of questions and until they are asked and answered, how can anyone define "The best place to be a diver?"
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To me, perhaps, the "Best place to be a diver" is the Yucatan Peninsula -- but not everyone wants to be able to dive in shallow, warm caves to rinse off the salt from a pleasant reef dive -- but even that area has severe negatives.