To me, until I see data that says otherwise (and maybe it's out there, if so point it out to me), the QB sneak under center is NEARLY ALWAYS the best play to run if you are going for it on 4th and 1. If you are passing it on 4th and short you are willing shooting yourself in the foot as far as converting goes, by about 9-10% every time. The evidence below relates to the NFL, but I would guess it more or less holds true in college football as well.
Evidence: http://www.sportsonearth.com/article/62665328
http://archive.advancedfootballanalytics.com/2011/11/qb-sneak-vs-rb-dive.html
Absolutely. Any handoff takes time that a QB sneak doesn't, and any pass has an inherent risk that runs don't.
Also, relevant to the OP, Nebraska ranks 63rd in passing yards per attempt (7.0).