Fallout 3 or New Vegas?

Fallout 3 is ok, New Vegas kicks ass hard though.

Fallout 3. Cant say anything much about Vegas since I only have it on PS3 and its buggy like hell. But I heard its awesome as well!

Fallout 3. Just for atmosphere I enjoyed more than in NV.

Both are good. And you seem to have missed the sale. I got both of them, complete with everything (GOTY/Ultimate), for something like 7 bucks :-P

Keep an eye out though. Paying full price for these is not smart, as they go on deals quite often, dirt cheap.

New Vegas, big map, many weapons, and history.

I tend to say that F3 got a better world for exploring while NV got some imrpovement to gameplay and better writing etc. But you should get both and mod the shit out of em :)

New Vegas, no doubt about it. It has better combat, better quests, more replayability, no stupidity (unlike FO3), etc.

Fallout 3 first.

Vegas by far - better atmosphere, characters, writing, plot, gameplay mechanics, companions that have more to them than just being pack mules. Also absolutely fantastic dlc.