Takeoff briefs are different from Px briefs. You discuss the takeoff, what you are going to do, what to do during the possible malfunctions or emergencies that you might encounter. The key is to make sure it is appropriate for the situation. Obstacles, weather, performance, weight, terrain, etc, can all make the ideal response and outcome different. So you carefully consider these things and brief your plan of action, so that should something go wrong, you'll have a higher chance of doing the right thing.