Some depends on how many beers you normally have fermenting at once. I've got a mini fridge build that I basically just extended the door on, but it only fits one carboy. That's fine for me, since I really only need the temp control for a week or two, and if I have a second fermenting beer I need to control I toss it into a swamp cooler. If you build out a chamber like govner1 you can do more than one carboy, but requires at least a small bit of handy work.
Another thing to consider is that a chest freezer is easier to control for lager temps if you'd like to go that route. While my mini fridge works great for ales and for moderate cold crashing (50 degrees or so), I lose a lot of cold air once I start trying to go down colder than that for any extended period. Also, I think it depends on the temp outside the chamber, but I'd imagine that the chest freezer is probably cheaper to run, since its built to get down to low temps fairly easily, where a mini fridge isn't intended to have to go too far.
One last thing, having noticed that you're in Florida, is to consider humidity controls. I know my chest freezer kegerator tends to build up condensation fairly easily, and its a pain to get into the bottom to dry it out. When it happens in my mini fridge its easy to open the door and wipe everything down. Not saying that should be the deciding factor, but you may want to look into some dehumidifiers if you go the chest freezer route.