JImbo's criticism's have been of his offensive style/play calling. His critics label it as a system that worked up until we saw college football spread out and its pace quickened.
Petrino's success was found in his offensive style in the same period Jimbo's style of offense was successful. It was unique and difficult for some teams to prepare for—like seeing a defense prepare to face a triple option attack. His offense isn't unique in today's game. He'll have better athletes, no doubt.
Out with the old, in with the well worn.