I do not envy Butch Davis in having to make this decision.
First, the tale of the tape:
The statistical comparison is basically equal since there are any number of caveats you can throw out there to account for the differences. For example the rushing average with Sexon is significantly lower until you realize that includes a 35 yard game against Miami. In the four games since UNC has actually run the ball slightly better than they did with Yates at QB. Yates has generally been a better passer in terms of yards per game but again you have to account for the fact that Sexton lost Brandon Tate during the Notre Dame game and endured the transition of offense in the UVa game. In other words both QBs have offered the same production both in terms of points and wins though you could argue that Yates is not responsible for the VT loss since the Heels were leading when he went out. Then again can Sexton really be held responsible for the loss at UVA? He handed the defense a touchdown lead with two minutes left and they blew it. The only real negative for Sexton is the three INTs versus one for Yates. Then again that is four INTs in eight games total which is incredibly good in terms of playing mistake free football.
If the basic stats are the same that means the decision is going to rest in the realm of the intangible qualities. You also have a fairly big question of how much rust Yates has and whether you can afford to waste a few possessions to help him shake it off. I would think not since UNC has to win all the remaining games to have a shot at Tampa. I doubt there is any kind of chemistry question. The offense will probably respond to either guy and as far as I know Yates and Sexton get along since the former was very active in helping the latter during the game. There is also the loss of Tate and the emergence of the running game. Sexton has worked through the major shifts in the offense to its present form whereas Yates would need to adapt to some obvious difference in how the offensive unit functions now versus five weeks ago.
In the end, I am not sure there are any logicial or factual reasons that can be tossed out there in distinguishing the two. It is my suspiscion that Davis will make the call on some kind of "gut" feeling or on the basis of some factors only he, as head coach, can account for. I do not think UNC can go wrong with either player unless Yates is completely out of sync which would make putting him in the game an immensely bad idea. So the chances are Davis will split the difference and approach it like he did versus Miami giving one player the first two or three offensive possessions followed by the other one then proceed from there.
It is a tough decision for Davis and one I am glad I don't have to make.