Miami has a öööö ton of northern transplants. Miami would probably fill the stadium when Ohio State, Penn State, Michigan, Wisconsin come to town and the other games would draw well.....Iowa, Illinois, Oregon, USC, UCLA. Tallahassee is just a smaller redneck town.
Miami is an international destination city. I could totally see the BIG10, with both teams on the table, choosing Miami. With BIG10 cash, Miami might finally have the motivation to build a tight 40k to 50k stadium somewhat near campus - it would be expensive to buy the property and get zoning, but it could be done. The actual building of it would be the easy part, acquiring the property and zoning would be the hard part. Lots more BIG10 fans in Miami than Tallahassee. In fact, even UCF makes more sense to the BIG10 than FSU - if you want your northern transplants at games.
Same for GT. Metro Atlanta is a huge, untapped, BIG10 market. It would absolutely help the BIG10 schools with recruiting to be able to play at our place and occasionally at MB stadium. Looking at it that way, we make more sense than FSU.
That said, I don't know what is in the minds of the commissioners and boards of the BIG10 and SEC. FSU is something shiny in a ööööty town that is a PITA to get to and expensive for visiting fans for what you're getting, ööööty Tallahassee. Atlanta and Miami and even Orlando are destination cities where there are actually things to do outside of going to the local ööööty college bar or shop at the ööööty strip shopping center.