A lot of it depends on who Gill could have gotten to be his defensive coordinator. The Nebraska DC is a good enough job that I think Gill could have pulled in some elite talent. As for offense, I think we'd be fine on that side of the ball too. Regardless of who he got as OC, Turner's finger prints would have been on the offense. (Just like our defensive identity was Bo's these last few years.) I think Gill would have put an athletic QB in place, and run a good balance between run/pass.
Gill would have been a better recruiter than Bo. By a long shot. What parent wouldn't want their kid to play for Gill? The guy is a saint. That said, some of the things he did in Kansas were a bit overboard. The 10:00pm curfew against being with women? Oy! That just wasn't a very good move. Still, even the curfew things wasn't doesn't compare to Pelini's profanity tapes.
Re the OP's question: I think Gill would have done better than Bo. Gill had three years of HC experience under his belt at the time Pelini was hired. And a ton of experience at various assistant and coordinator positions. Gill would be able to pull in athletes. Texas was his home, which wouldn't hurt. Gill would have been a MUCH better face for the program than
Bo.
Would he have been a better recruiter though? I don't think anyone would deny his character, but Bo did have a championship ring, a reputation for being one of the best defensive minds in the country and a decent coaching career. That seems like a pretty good pitch for kids, and we know the players always loved Bo, which I'm sure was a big sell for recruits. I don't know, just playing Devil's advocate really.
I can't deny that he would have been a much better face for the program, but, I think Gill's success would've been VERY dependent on his staff. Who he put in place to help him succeed and how talented they were. I think he MAY have done better, but, there's so just so many questions surrounding this hypothetical. He went to a place with less resources, less talent and less support than Nebraska and just completely tanked. He obviously had disadvantages but it's still a bit of a red flag to me.
I think the same thing about Turner and Bo now that I did back then - in 2008, they were both a bit too young and inexperienced to be the head coach here, in my opinion. We were banking a lot on Bo's development as a coach and bringing in a good staff to compliment him.