You might lose the UNC and Duke basketball match ups, but you gain a natural football rivalry with Penn State.
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Maryland fits in nicely with Big 10 basketball. A team that is on the rise will gain credibility competing in a much better basketball conference. The Big 10 is not a two team basketball conference. OSU, MSU, Michigan, IU, Illinois, Purdue and Wisconsin are competitive program and you still got the ACC v Big 10 challenge. Plus Gary Williams is an analyst on the Big 10 Network.
I know I'm biased here since I don't really pay attention to college football all that much. But if you take a random sample of Maryland fans (whether they be basketball, football, or both), I would say 90% of them would rather keep the Duke rivalry game than develop a rivalry with Penn St. football.
Also, the ACC is a 2 team conference? That just isn't true. FSU has been competitive for at least five years. NC State appears to have re-found their program. And the conference adds three perennial contenders in Notre Dame, Syracuse, and Pittsburgh. The Big Ten is certainly a very very good basketball conference, but the ACC still reigns king.