For whatever reason (perhaps due to the fact that Missouri is all but offering Jim Delany a blowjob to join the conference), Missouri is getting significantly more credence as an expansion candidate than Nebraska. Perhaps it was this?
Regardless, I see Nebraska as a more attractive all-around school, as it is ranked (overall, not as a research or graduate degree institution) slightly higher than Missouri by US News and World Report. In addition to academics, in terms of athletics, I don't see Mizzou as surpassing Nebraska at any point in the near future in any sport other than basketball, which in itself is a rather low-grossing (and ergo, low-importance) part of the Big XI expansion conversation.
My personal ideal expansion scenario?
12--Nebraska (not terribly unlikely, either, even if a 12-team league is unlikely enough)
13--Texas and Texas A&M (the chance of a 13-team expansion is as likely as Al Gore buying a Hummer or R.C. Soles or Dick Durbin joining the NRA)
14--Nebraska, Texas, and Texas A&M (but a three-team take from the Big XII seems rather unlikely, even if it is a Big XI man's wet dream, in the words of BornAHawk)
15--Yeah, right
16--A 16 team Big XI? Why not just establish One World Government and call it a day? No way the Big Ten expands this much.