The unique thing about the NFL is the fact that every team has their own identity for better or for worse. The environment that an NFL team plays in tends to dictate what the philosophy will be for the team as well.
For example, if you are cold weather team, your identity might be one that is physical on defense and run the ball on offense due to the fact that throwing the ball in cold and windy weather isn't always ideal. If you are a team that plays in the warm weather or in a dome, you might gear your team to be a high tempo offense with a lot of scoring.