I really don't think the ND decision was a result of the choice b/t Michigan and Purdue/MSU.
I think it was a choice b/t Michigan and Tex/Bama/OU/FSU (a rotating big time team). They realized that even a pseudo-quasi conference committment-ish substance won't allow for them to play as national a schedule as they'd like.
Now, I think that pretty fucking short sighted considering that the ND-M game gets more national attention than many of their committments (basically all of them but USC), but w/e you can't trust dem catholics. #gordongee