Allocated seating and staged boarding is more likely to be faster than a free-for-all if the preferred seats are near the front, because you'll have everyone stood just inside the aircraft door putting their bags up in the lockers. The only time you have problems is when everyone gets to choose their seats and a family with small children finds it can't get a group together because all the aisle seats have been bagged. But then with free-for-all they can end up in the same situation.