Having read various articles and books on acclimatizing I found that sleeping at the trailhead has no benefit and actually is detrimental. I think Medicine for Mountaineering talks about this. When you sleep your respiration slows down which hastens altitude sickness. By sleeping low you get more oxygen during this period of rest and it helps during an summit attempt.
It also takes a few days for your body to start acclimating so one night at the trailhead will not help you.
As for living high and training low it's really the same thing in reverse. At lower elevation you get more oxygen during times of high exertion. By living high your body gets accustomed to using less oxygen and so the extra oxygen during training helps your performance.
I've done Whitney where I've slept at the Whitney Portal to get an early start but I think next time I'll get a hotel in Lone Pine. And one the next night so I don't have to drive home right away. It's not that long of a drive up and I won't have to break camp in the dark.
One time we drove up from the desert, slept at the trailhead (getting there about 11p.m.), did the Mountaineer's Route and drove home (getting home about 11p.m.). Then we went to work the next day. I don't think I'll do that again.
So, lower elevation means more oxygen which is good for sleeping before a big climb and training for a big race.
