> There's nothing efficient about big cities. Hours of commuting by millions of people every day.
You have it backwards. Density makes mass transit feasible. You want to talk about commute times, spreading everyone out is going to magnify that.
Cities are efficient. At least, they can be. Busses and trains/subways work a hell of a lot better in urban cores than suburbs, and are effectively worthless from an efficient standpoint for moving individual people in a rural environment.
