For the 2009-2010 season it was the Pittsburgh Steelers in terms of points, and the the San Diego Chargers in terms of yards allowed.
Steelers--period
which nfl team runs a 4 3 defense
The Pittsburgh Steelers. No question about it!
Steelers and Ravens
Brian Urlacher
probably the steelers.
Dallas Cowboys Best Team
Currently, they are not the best team in the NFL.
The Boston Celtics have the best defense because you need defense to win championships and they have 17
The New York Jets had the best last year, though the best defense in the league statistically shifts every season.
Pittsburgh http://www.nfl.com/stats/team
The San Francisco 49ers