Hi there,
I'm in a pretty similar position, except with The Commonwealth Medical college, which is another brand spankin new school. Yesterday I decided to go there, and I will tell you why, maybe it will help you with your own choice-
I think there is alot to be said for being the first class. I believe that FIU's class is very small the first year? Which= alot of personal attention. Having the Dean know you well, and have a special place in his/her heart for you because you were a member of the charter class will be HUGE when you need recs for residency.
It wont fail. There may be bumps in the road, but the LCME works hard to keep new med schools moving ONCE they have their provisional accreditation (which is the hard part to get.)
Money! It is a big deal ot have less debt when you graduate- you will be more able to choice your specialty based on your interest, and not on what will pay you most.
Lastly, think about it from FIU's point of view- they WANT to have a great reputation, so they will do whatever it takes to get their first class into amazing residencies. You'll be lucky to have such a strong force behind you.
Hope this helps, and good luck!