Mojave is a....you know...desert; in fact I was expecting large area of nothing and just odd sand predator between locations.
Fallout isn't about farming loot cattle you know
This was actually one of my only few complaints, especially since they blocked off a third of the map on the west and some on the eastern borders, and everything is concentrated in the middle third of the map for the most part... you can call that whining if you want, but frankly if you're going to put land in the game then use it, stretch out everything so it's all a bit more spread out. But don't just block it off so I still get to enjoy it eating up memory/ram by the fact it's part of the landscape, while otherwise being useless.
It's a present to people creating MODs, who want a wide area to add their own towns and the like. A desert needs to feel barren. This was supposed to encompass, what, parts of 3 states?
Personally I don't think either game was much bigger than the other, but if FO3 felt bigger it was because there was a little more distance between things.
That goes doubly so considering that, as someone else already mentioned, about half the buildings cluttering up everthing are just boarded up scenery that is otherwise completely useless. And I think I'm being generous with that figure.