I personally was not happy with the MIA station when I did the FL driveout 2 summers ago. You can search the forum and see my account of how they did not want to honor my rate, in fact did not even know about the FL driveout, did not speak English very well, and gave me the worst car they had because it was a one-way. (Although to be fair, that last point is quite common, especially from offices in larger cities.)
I have not rented from a neighborhood store in the area, so I can't give you an accurate recommendation about the quality of service. But next time I'm in Miami, I most likely will.