The more I think of it it's these little execution plays - the simply check down, always gaining positive yards and not shooting yourself in the foot, that add up to make the difference.
Take Brady, he's won 4 Super Bowls by 13 points. He's plus 6 points in 6 Super Bowls with a 4-2 record.
Now back to Monday Night's game: IF Leodis doesn't fumble (Pats fg -3 pts) and Carpenter kicks a field goal (Bills fg +3 pts), and Mario chips the running back which enables a Corey Graham tackle the Pats settle for a field goal (Pats -4 pts). Those plays in our favor make the score 16-13 Bills. That plus 3 points is the Brady margin in Super Bowls.