Miami would make a lot of sense for the Big 10. They've cleaned up their academics which weren't all that great in the 80's and 90's to now under Shalala and they're steadily becoming a research powerhouse as well. Miami is by far the best college in Florida academically. The Florida research "big 3" is now UF, USF, and Miami. Now if only USF had some football history, they could be a B1G target as well...
Thats pretty subjective.
There are all kind of metrics to base such a claim. Once you agree on metrics, you go from there. Academically, its hard to not say its New College. 87 percent of graduates being accepted into masters and Ph.D programs, 85% into law school, The Wall Street Journal has it as the #2 public feeder school of elite law, medical and business schools. 1/3 of all their science grads since 1967 hold either an M.D.. or Ph.D.
I was going to say New College, but its a small school that most people never heard of. If it were just the big schools on overall terms of incoming students and their outcomes from those schools(i.e. grad/employment rates), UF is the best college/university in FL. Miami is 2/3 depending on COL.