So I have some insight into both programs from my opportunity to interview at them/ knowing med students at both schools, although I don't attend either.
I personally would pick OUWB if costs were equal.
General Thoughts between the two.
Cost of living in miami sucks but tuition is cheap if in state (although were considering prices equal). OUWB is cheaper living, but out of state tuition for all.
Diversity: FIU is incredibly "diverse" but I would argue at OUWB is by no means monolithically white/non-minority. In fact most of the student I know at OUWB would be classified as underrepresented minorities.
Location: While Miami can be fun, its also can be incredibly crappy. Hot 24/7 which is awesome when you're enjoying your post-exam party on the beach, not fun when you have to be professionally dressed in a coat while the heat index is at 101. Miami also has the worst traffic I've ever seen meaning what is a 15 minute commute in other parts of the country becomes 45 minutes. Michigan is beautiful during spring and fall, but you'll have to deal with snow.
OUWB location is about 30-45 minutes from downtown detroit which is a very cool area to have access too. Normally I wouldn't consider this a short drive, but seeing as driving times in miami seem to be double the norm, it really isn't that bad compared to opportunities in miami.
Rotations:FIU's aren't terrible but aren't nearly as good as OUWB will be. OUWB healthcare systems is their own and they offer nearly every residency program available, FIU has limited sponsorship of residencies, and shares their hospitals with MANY SCHOOLS including Nova, Lecom, FAU, and several carribean schools. As such quality of M3/M4 year go to OUWB.
Step: FIU has some of the highest step1 scores in the nation, which is due in part to taking the step later than normal (M3 vs M2) as well as a overly oppressive review of students progress. What this means is that if your at the top of your class, you'll likely kill the Step and be set up well for competitive residencies. Those towards the bottom of the class may be forced to repeat a year of medical school even if they have all passing marks (this is what I was told by several med students during my interview at FIU). While this forces all their students to do incredibly well on step, it can be a disservice to someone wanting to attend a less competitive residency like family medicine as they will essentially incur an extra year of school for nothing. OUWB doesn't have this rigorous review but i'm 99% sure their scores aren't anything super extraordinary like those touted by FIU. In short, FIU is gonna make you a superstar step taker whether you like it or not, OUWB perform competently and are average compared to other schools.
Curriculum/grades: slight differences. Pretty sure no gross anatomy dissection at FIU, def is dissection at FIU. I remember everyone at FIU hated the ethics/ diversity/ social inequality courses because at the end of the day it boils down to the same few concepts and takes an enormous amount of time out of your day. Most at FIU also expressed frustration with the community program because, although it is incredible in concept and has the potential to truly serve the public good, the realities of treating these populations are much more difficult in practice and faculty/administrative support isn't as strong as it should be.
Grades at FIU are exact (you get an 88 in anatomy, not an Honor/pass or A,b,c.) furthermore FIU passing marks aren't preset but based upon statistics i.e. they pick a standard deviation below mean and make that the cut off. OUWB has hard cut offs (i.e. everyone who gets a 70 passes.) Some like this because what you get is what you get. and theres no rounding out. "Why should your 88 in anatomy be equivalent to someone else's 75 or even 86 shouldn't you get acknowledgement for your hard work instead of receiving a passing grade like everyone else."
One thing i dislike about OUWB is that they have an Honors, Pass, Pass with remediation, fail scale and require attendance to get Honors.
Other stuff: both programs have some sort of capstone/research outreach built into curriculums. Both facilities are pretty nice. (I may like OUWB slightly more but simply because they have that giant lounge area).
FIU does have a Cool Hogwarts like program that sorts you into a "house." Love the student body relationship and collaborative environment this program fosters.
Overall your choice. Both seem to be doing very well in residency placement for how new they are. Can't go wrong either way.