So I am a Pats fan, which means I would love or Brady to be the clearcut best ever.
I don't know if you can easily make that claim though. It's hard because football is just not an individual sport, despite media/fan attempts to make it that, and any attempts to make it such are doomed to fail. Not only is a qb on the field for less than half of a game (defense and special teams) but on offense, though he is the most important player, there are still 10 others on the field at the same time.
So people can say that manning would never have thrown that INT bomb in the pats-ravens game, but on the other hand Manning has never had the lousy WRs at creating separation that Brady has had for the bulk of his career. Except for 3 years or so of Moss, Brady's receivers have been unable to create any ounce of separation on their own, and their patterns are generally short and based on design and timing. Very difficult. Manning can do this too, of course, but he also was known for if he had any more than 4-5 seconds, Harrison and Wayne would just be wide wide open for a bomb.
On the flipside, people can say Brady won 3 superbowls, but really the Pats did. Back when they won, their defense was very very good and they had an incredible kicker. Better than the colts' respective units. If Manning has that defense, he probably has a few more superbowls.
To switch again, people talk about stats and Manning over Brady. Couple points. First, for the first half of Brady's career, he was saddled with extraordinarily average pieces on offense. Just not an emphasis of how they built their team. Never the case with Manning, who was always stacked on the offensive side.
Of course both teams were great at keeping their O-lines intact and at a high level compared to many other teams.
How do you possibly quantify those things into a head to head comparison in a game that has 50+ on each roster? It's an impossible media construction.