One point that hasn't been mentioned but I believe to be very relevant is this:
FF by the exit - opens it, gets out and then legs it, as fast as they can.
Crew of any kind or airline by the exit - opens it and then assists passengers through the exit, either from inside on, say, B747 or from outside on a B737 because that is what they are trained to do.
So it is a no-brainer really, if you have crew paxing then put them by the exits to improve the overall level of safety should an accident occur.