re: How is Big 12 adding Memphis/Cincy any different than B1G adding Marylnd/Rutgers

Maryland and Rutgers are AAU universities with an extremely strong research profile that fits into the ethos of the Big 10. They may not have extensive football histories, but the rest of their athletic programs are a good fit. Plus, their football teams are certainly competitive with the current level of play in the Big 10. Most importantly, they nailed down important TV markets in Washington/Baltimore and NJ/Philly.

You're right that some of the teams that have been mentioned for the Big 12 (like BYU, UCF, and Boise) wouldn't water down the league in terms of football. However, there are additional considerations. Do the current Big 12 schools want to send their non-revenue sports to Provo, Boise, and Orlando? That's a lot of money. UCF and Memphis may provide an entry into an excellent recruiting market, but few of the other schools do. Can the other universities bring anything to the table in terms of research prestige? We like to pretend this doesn't matter, but it matters a great deal to the presidents and boards approving these conference moves. Some of the universities for the Big 12 that have been mentioned provide a strong undergraduate education, but none have a strong graduate school/research reputation.

These decisions have a lot of moving variables. That's why the Big 12 is reluctant to move immediately.