he has taken his teams to 18 bowl games, compared to 15 for Whittingham. And he's done that at programs where he was building or re-building.
Whittingham is a couple years older than Leach, and has been at the same school his entire career. He started with a huge boost from Urban Meyer at a mid-major school.
Total wins are hard to compare (Leach has 158 to Whittingham's 153), but they came under much different circumstances.
I could see giving the nod to Whittingham, but also I think if a school were looking to hire someone to rebuild, Leach would be the pick because he's 3-0 in rebuilds and Whitt has never coached anywhere else.