When a the best defensive team makes it to the Super Bowl, that team always wins and it is often a blowout. When 2 top defensive teams meat, it is usually close and low scoring. In Super Bowl V the Cowboys Doomsday Defense was almost legendary. They faced the Colts, which many believed had a better defense than Dallas played what was called the "Fumble Bowl." It wasn't that the offenses were bad or played a particularly bad game. The Defenses just controlled the game.