Pro: Defensive mastermind
Bill Belichick coached the New England Patriots for 24 seasons and the lowest his defense has ever ranked in points allowed per game is 17th which happened in 2000, 2002, and 2005.
When you dive in deeper, his teams have been top ten in points allowed in 18 of his 24 seasons and have been top five nine times. That is remarkable. For reference, the Falcons have been top ten only four times during that same period.
When you hire Belichick, you guarantee that you will have a good defense. No coach in the NFL schemes up a better, more adaptable defense than Belichick. It is something you can count on.