Debby makes some good points as always - I'll add some info:
That time of year is iffy due to the wind that can accompany cold fronts that come down from up north during the winter - while they don't bring snow, they can ruin diving if the wind blows strong enough - no way to tell right now, but be aware you stand a MUCH better chance of being blown out in Dec - early April than you do June - Sept. Just something to keep in mind.
(I'm not even going to touch on what could happen if the currents take the oil spill - which has NOT had any effect on the Keys or S. FL as yet - this way - we are all praying).
In MIA, the only real option for boat diving is RJ Diving Ventures - excellent op, BTW Located in Miami Beach - too many to mention in the upper Keys; do a search as this is likely the most asked topic.
Forget shore diving in the Miami and the Keys - its bad, as Debby points out - places do exist in Broward and Palm Beach counties, but they are not real close to the places you are talking about staying. A boat is really your only option if you want to see a reef or a wreck, unless you plan to travel 100's of miles to see sand and turtle grass.
Cigars.....hmmmm I love 'em - the best local place's at the best prices are Mikes Cigars, and Neptune Cigars in the Miami area - both have web sites too - because its a popular habit down here, the vast majority of the shops are very good - the ones I mentioned have the best prices (and I do 2 per day).
Re rum, this is (I know its easy especially for us residents to forget) America - Barbados or St Thomas its not - any bar will likely have what you want.
Having dove Hawaii and lived in Miami for 31 years, all I'll say is that they are vastly different places - apples and oranges - I could make a list of the pro's and con's of both, but really that's for you to decide. I love S. FL diving - but all things being equal, I think Hawaii is really unique but likely to be more expensive, time consuming, etc.
You have a ton of info at your fingertips - do some searching and you will get a TON of info about both locations.