FO3 demands plot at every turn as soon as you start in. It feels more linear because, shucky darn, you've gotta find your dad and everything scales to your level! let's go save dad!!!!

NV refuses to stoop to your level. It will punch you in the face if you don't know how to block it. Your goal also isn't thrown at you 24/7, so you have reason to explore and enjoy the beautiful Mojave wasteland.

That said, they're both good games! I just like NV better because the mechanics are more polished, IMO. Repairing weapons, no "Big Guns" skill, etc.

New Vegas is generally more civilized that FO3, that's the big difference i saw.

NV is the better game when it comes to features, but Fallout 3 had much better atmosphere IMO. Wandering a desert just doesn't compare to navigating the DC ruins.