I voted Independent Vegas. Obviously a Legion victory wouldn't be particularly great for humanity (to name a few reasons, fascist dictatorship, slavery, military-centred society) and while I like the NCR I also think they deserve to be slapped around a bit. Not all out destroyed, of course, but they need to learn ways of cultivating their civilisation without expanding into other people's territories and basically repeating the mistakes of every nation preceding it. Maybe it would be a good thing for America to be enveloped by the NCR. I mean, they have decent enough values, but they haven't learned from the mistakes of the past. They essentially want to rebuild the world that eventually blew itself up.
Mr House and Independence promise a new beginning for humanity: one more technologically-driven in its nature. The only problem with it, at least with the Mr House ending, is Mr House himself. Really, there is very little difference between Mr House and Caesar. Both are psychopathic men who care more about their own narcissistic vision of humanity than they do of humanity itself. Mr House doesn't care about the people of Vegas, he only cares about Vegas itself. It's why the snowglobes are in the game. They're a nice visual metaphor of what House wants. A frozen city, designed exactly the way he wants it. The fact that he doesn't care about the White Glove Society being cannibals should set anyone's alarm bells ringing.
So I would argue that Vegas, controlled by an artificial intelligence, is the best option. It lacks the narcissistic personality of House but still promises to continue his vision of a technological utopia.And if anything, Vegas being run by a smiley face is amusing to me.
"It's 106 miles to Arroyo, we've got a full fusion cell, half a pack of RadAway, it's midnight, and I'm wearing a 50 year old Vault 13 jumpsuit. Let's hit it."