Some USA Today reader commented "There is no way Brady would ever throw an egregious interception like [Peyton Manning did in Super Bowl 43]."
Does Tom Brady really have ice water running through his veins? I'm not convinced. Consider these incidents that come immediately to mind:
1. Super Bowl 42 was his worst playoff game to date.
2. In the playoffs vs. the Ravens this year, he was even more spectacularly bad.
3. He threw a pick at the end of their away game vs. the Dolphins this year
4. He chocked on 4th and 2 against the Colts last season
5. He fumbled the ball to lose the Tuck-rule game; only a gift from the football Gods saved his season
and of course
6. Marlin Jackson picked him off to seal their loss vs. the Colts in the 2006 AFC Championship Game
It turns out that if you look at win probability and expected points added in the playoffs, Manning is better than Brady on both counts (since 2000 when data become available).
Manning: 3.59 WPA and 114.8 points
Brady: 3.26 WPA and 62.1 points
There are a few things worth pointing out. First, a year ago Brady did have better playoff numbers--but Peyton's whipping of the Jets and his strong performance in Super Bowl 43, along with Brady's collapse against the Ravens, flipped the script. Second, there biases here: (1) Peyton's first playoff game, which was not spectacular, is left off and (2) Brady played more of his games in the inhospitable climate of New England. Also, a lot of Peyton's number are from 4 strong performances in blowouts over the Jets, Broncos (twice), and Chiefs. Finally, the sample size here is 17 games (Manning) and 18 games (Brady).
Brady seems like he is a more clutch player. Peyton looks like he losses his cool under pressure. But in the data its very hard to find hard evidence for this hypothesis.