I chose the Kings for pretty the much the reasons stated so well by Longknife (btw, kudos, Longknife). The Followers are fine, but they'd never survive on their own without getting bogged down trying to just stay alive.
I'm also fond of the Great Khans. One may look down on them for their drug making activities, but the fact remains that the drugs they produce are functional and often needed, if not absolutely necessary. To blame them for the behavior of the fiends is like blaming the Gun runners for the abuses of guns that occur throughout the game environment. My only problem with the Great Khans is simply that they don't really stand for anything meaningful.
Oh, and about living conditions in the Lucky 38... that place gives me the creeps, and between the feeling of a vanished population along with constantly moaning wind, I think it'd drive one crazy fairly quickly.