I did my undergrad at USF, so I can mostly speak of what I know from having friends as undergrads at UM and Barry. I did explore Miami's program last year and spoke to the admissions director there, but ended up not applying. A lot of it comes down to how independent you are. UM is a great school and obviously has a certain level of prestige, but I don't think it's much of a formal program except for receiving a committee letter. Your classes will be large (100+) and you will of course be vying with undergrad premeds for attention from professors and advisers. As far as I know from admissions, the postbacs basically did the same thing as everyone else (you don't have a separate adviser, classes, MCAT prep, or anything like that). The main downfall of UM is the price, which is beyond exorbitant and what I consider very little value for what you're paying. If they had a linkage with Miller, it might be worth it, but otherwise....it's a tough call.
Barry is smaller, but I don't know much about its postbac program. I doubt it is very rigorous, and it is definitely nowhere near the rigor of UM. The upside is the personalized attention you could receive from professors.
If you are intent on staying in Florida, I honestly think you're better off doing in-state tuition at a public school near you. Going into massive debt over either of these programs does not seem worth it. If money is not an issue for you, though, that changes things entirely. These are just my two cents; obviously, if anyone has actually been through either of these programs their opinion will be more valid.
