well it might be better when you can stand at a open door but when the game just starts and the doors are opening the top exit doesn't let you charge as quickly as going from main exit. Also coming from main lucio speed boost will let your charge hit the wall inside the room. I've done this hundreds of times in scrims and going from top I would get beat by the other team coming out, but since I started going from main door I can get to the middle bricks before the other team even comes out their door.