Miami boasts a fast paced, multi-cultural party atmosphere. There is a an abundance of wealth and a lot of poverty. It's certainly a more upbeat, late night kind of place. I can't speak for schools, etc. but my impressions of Miami the two times I've visited, is I would be hesitant to relocate my family there. Our Miami OSO friends can shed more light on this, though.
Tampa/St. Pete is a more laid-back place, but equally full of fun and things to do. The beaches are great(some of the cleanest and best in the nation) and the boating is top notch. The gulf is pleasant and usually quite navigable. The cost of living is probably quite a bit less than Miami also with taxes and insurance. Most of the schools around here are rated A's and B's(Florida school ratings), crime is low and people are great. There are plenty of on-the-water eateries and very many boater friendly facilities.