Since Bush is notoriously loyal to his cronies, the question is somewhat problematic. Based on his history, though, I can make one guess and that is that Libby is significantly more competent at what he does than is George. Bush’s loyalties are strongest toward those that can’t make that claim — i.e. Gonzalez, “Brownie”, Mineta (now there was a REAL jewel) Chertoff, Miers, etc.
From what I’ve seen of Chertoff he wins the Bush Freakshow Prize.