I stand corrected...my eyes must be getting old and the columns of stats were running together. You were right, their winning percentages are higher. It is not really apples to apples with those players like it is with Manning and Brady. I tend to agree that winning percentages don't tell the entire story.
But...
Peyton's career winning percentage is .687. Heck throw out his 3-13 rookie year and his percentage is just like Brady's at .762. They both win at unprecedented levels, but his playoff percentage .450.
Brady's career winning percentage is .777, and his playoff percentage is .739.
There is no drop off with Brady. He essentially wins at the same rate that he would otherwise. There is enough of a sample size with each QB having played at least 20 games unlike Dilfer.
Truth be told we are splitting hairs. Statistically there is not much difference. Both have a command of their offense like we have never seen. Both are in the top 5 QB's of all time. Peyton was better earlier in his career, Brady has been better later in his career. We get to watch greatness every time they play, and we should just enjoy it.