One thing that's very, very rarely mentioned in these arguments (I only scanned about 8 pages of this thread but didn't see anything mentioned) is that Manning plays in the comforts of a dome stadium, plus a few divisional games every year in domes as well. He typically plays 2/3 - 3/4 of the year in a dome. Meanwhile Brady plays in a dome once or twice a year, period.
The difference in stats across the two is stark, and it isn't just Brady and Manning. Hell, look at Favre this year. To prove how under-reported the dome effect is, I searched a number of sites (pro football reference, ESPN, CNNSI, NFL.com) and couldn't find splits by dome/outdoor. Field conditions tend to be better and you never have to play in 'weather'. It's a HUGE effect, especially late in the year when Brady is typically playing in freezing temperatures and often times in snow or rain. Cold, Hard, Football Facts had an article a few years ago (couldn't dig that up either...my search skills are eroding) that broke Manning's and Brady's stats down, dome vs. outdoor. And guess what? While Manning had the better overall numbers Brady beat him in TD/INT ratio, passer rating and completion percentage in both domes and in outdoor stadiums.
Note: this was done before Brady's remarkable 2007, so these numbers were from a period when Brady was seen as more of a great game manager but not one who put up gaudy stats.
Manning is a fantastic quarterback, one of the best of all time. However, he has spent over half of his NFL career in the comfy confines of a dome, and that just has to be taken into consideration.
