I could see both sides of that argument, but I think for different sports.
In basketball (both men and women), I think that there is no doubt that we fit better in the ACC. The Syracuse and Pitt rivalries would be restored, along with our ability to pick on BC 23 games in a row, and additionally some big-time matchups again with Duke.
In football, however, I think that we've had a much better rivalry with Rutgers than we did with Syracuse, Pitt, or BC (although admittedly, the BC rivalry has great potential). If you add in the fact that the Maryland battle could turn into something more, due to the last two years and the fact that Randy is still their coach, and I think the B1G makes more sense from a football perspective. It almost certainly makes more sense from a cultural perspective, since I doubt that we'll ever truly fit in with Clemson, Fla St, Miami (yeah, I know they were in our league before), Georgia Tech, Wake, UNC, NCState, or Duke...