Yards per point differential is a commonly used statistic by weekend and professional handicappers. It gives an idea of the strength of a team's offense versus their defense. For the offense, a lower number is better...for a team's defense you want to see a higher number. Ideally you want to use a minimum of 4 games played for this calculation to be useful, it's often used in playoff selections because it uses an entire season's worth of data.
More about Yards Per Point (YPP) Differential
For the offense, a lower number gives a indication that the team makes the most our of their possessions by scoring points. For the defense, a higher number indicates that it defenses allow yards against, but they do a good job at preventing points scored (they usually have a good red zone offense as well).
This statistic is very telling, but there are a few drawbacks. It ignores some very important other factors in a football game - turnovers, special teams play, and starting field position.