Stating the obvious - we can't be picky about which lifeboat we get in...
Having said that, it is just as obvious, that the B1G would be our dream lifeboat. Doesn't look likely in the short term, however.
As between the ACC and the Big 12, I think a properly structured Big 12 is superior to the ACC for a couple of reasons. While, the ACC provides logistical advantages, I think instability down the road is inevitable. The gulf between the current football powers and the weak sisters (Syracuse, BC, Wake etc.) will only increase. The academic gulf is just as stark. Need I say anything more than Duke and Louisville? Further, the deal with ND will eventually bring divisiveness as the "full time" football powers wonder why they must win a conference championship to possibly qualify for the playoff while ND can cruise in with one less game and an inconsistent conference schedule. Simply put, the ND deal for full inclusion of the olympic sports, doesn't bring enough to the conference to warrant the sweet heart football deal. As posted before, the ND deal is a one-way mess waiting to happen.
In the Big 12, we would provide a connection to NYC and the Big 12 will tout it. Imagine a NYC BB doubleheader with KU, OU, UT and UConn. I think it works. Football wise, provided we can deal with the stadium issues, home games v. OU, Baylor, TCU, UT etc. would be big draws, easily as big or bigger than for an ACC game.
The ACC is going to become the modern day equivalent of the Holy Roman empire - it has shown signs of decay that will eventually doom it. Now, also on the "obviously" front, we would take an offer from the ACC in a heartbeat. But that has as much to do with being in a gulag than anything else. IMHO, the Big 12 has an appeal that the ACC is lacking. As between the two, I'd take the Big 12.