that on 747's with an upper cabin, you have pax lumbering down the stairs with sometimes 2 pieces of (heavy) luggage, not an easy thing to do under even the best circumstances. I have to tell you, I *really* appreciate having the FA's execise some traffic control ^ when we're all deplaning from 2L, and I'm crashing down the stairs, just barely able to stay upright while honchoing my rollaboard and carry-on.
And when in first, I really appreciate being allowed to scoot off quickly.
OTOH, I can't say I've noticed any significant impact when traveling in coach, and been "held back" while others trundled off.