Probably the most over played debate of all time, yet people get in near death battles over it. Truth is, they are nearly identical in regards to what you get. Almost frighteningly so. Since 2001 (minus 2008 when Brady was out)
Player Comp Passing Yards % TDs INT Rating
Tom Brady 2562 29,413 63.4 217 92 93.6
Peyton Manning 2752 33,032 66.5 245 106 111.7
So as the nubers go, Peyton gets the nod, minus INTs,
Notable facts, these stats start after Peyton had been at the helm for 3 full seasons, and Brady's first. Obviously there is a maturation process, and is indicated in Brady's later numbers, versus his prios. Second was tha absence of a big game reciever prior to Moss. No offense to Troy Brown and Dion Branch, but they just are not Reggie Wayne or Marvin Harrison.
On Manning's behalf, he does throw the ball a bit more, and that is reflected in his higher INTs. More attempts will equate to more picks. Also, for a number of years, he had the misfortune in lacking a competative defense. Always a QB's best friend.
Final conclusion, how can one say one or the other? Manning is a more natural in the pocket passer, and Brady is a better over all awareness QB in reards to denenses and shifts. But those tho aspects are impossible to quantify. Fact is, there are some 28 or so teams, that would love a Brady or Manning.