You want the whole story or just the 2002 part where Banks leads the team to an 11-2 record and was a late season candidate for Heisman. The part that you really don't want to hear is in 2001, McCann going 7-5 with 2028 passing yards, 16 TD's, with 11 interceptions (which is a bit high) Sounds like a guy you would pull for the new guy. Yes, in 2002 Banks led the most productive offense in the Ferentz era with 484 points (13 games) , but under McCann in 2001 the offense was the third most productive at 391 points (12 games).
SO TO ANSWER YOUR QUESTION, IT TURNED OUT WELL FOR BOTH OF THEM.
Had Banks started in 2001 it would have been over a quarterback having a good deal of success, without the benefit of learning Iowa's system, and without the benefit of having the game plan geared with his capabilities in mind. But of course it was obvious in 2001 how well Banks would do the next year.