It really depends on the teams involved and the location of the game. When deciding whether to bet the over or under, you have to consider the line, the offensive and defensive prowess of each team, and whether the game will be played indoors or outdoors in cold weather, warm weather, or stormy weather.
You can look at history, which will tell you the over and under have gone 30-38 over the past three years in the NFL Playoffs. However, history can't tell you what's going to happen this season.