^ @Beefy I peaked at your post. If you look more carefully at his stats and the specific games he "choked" in, you'll find that he wasn't actually playing poorly in many of them. He had a run of bad playoff games early in his career, but then afterwards his DVOA/AYPA/etc. were actually superior to Brady's. His playoff win-loss record is even better than Brady's post 2005, lol. Does this mean 2003 Brady > 2010 Brady? Obviously not.
I think "clutch" is partially a matter of luck. Manning and Brady are *better* than Montana in terms of their throwing mechanics, pre-snap adjustments, footwork, etc.