I prefer FO3, but I'm not hating on New Vegas, it's a good game (just not AS good). I have only had one bug, and that was solved 2 patches ago. My main beef with New Vegas is... I've done everything. Four times. I'm bored. I want to extend it, to keep playing! (afterall, it's going to be some years before we see FO4).
after I've played all the DLC? I'll go back and play FO3 again. Just to keep me going
(I don't feel the same drive to keep playing New Vegas, it's pretty boring once you've done everything)