While SI's Kerry Byrne said this stat came into existence in 2009, it's based on the quarterback's passer rating that we all know. The passer rating differential is a very strong predictor as to who will win the Super Bowl. From Sports Illustrated:
New Orleans finished No. 1 in Passer Rating Differential in 2009, the first year of the indicator's existence. That year, the Saints won the Super Bowl. Green Bay finished No. 1 in Passer Rating Differential in 2010, and they, too, won the Super Bowl. That made us two for two picking Super Bowl winners simply by looking at the Passer Rating Differential charts.
It was a treasure trove of data: the average NFL champion over the past 70 years produced a truly incredible Passer Rating Differential of +27.4 (82.3 Offensive Passer Rating vs. 54.9 Defensive Passer Rating). That's dominance in the passing game.
I didn't know the Packers had the best differential in 2010, but I knew Aaron Rodgers had a very high passer rating (No. 3 overall), and their defense kept their opponents to a very low one (No. 1 overall). And I'm not surprised that it was the reason for their success because the team is built on their strong pass offense and defense. The NFL is a passing league and being the best at passing and stopping the pass should be every team's first priority.