If you notice when Petrino talks about his ideal QB, it's always Lefors who at best had an average arm. No dropback QBs like Brian Brohm...
Petrino's play calling was significantly different (as it should have been) with SL. Took advantage of his mobility with the naked bootlegs and protected against his lack of arm strength with 3 & 5 yard slants and utilizing the TE more frequently. With all of the talent that we have at WR, I'm really surprised that Petrino doesn't find more ways to get them the ball in space with some easy throws for the QB - ie bubble / WR screens. It keeps defenses on their toes and makes them defend the entire field, and really tests their depth.
I remember the first game at Clemson - UofL gets Watson out of the game with that thumb injury and despite his replacement not being very arm talented - Swinney WR screened UofL to death. On one drive I think he called a WR screen 4 out of 5 plays - UofL couldn't defend it and it wore the defense out. Anyway - JMO.