As many people have said New Vegas has a better story with multiple endings based on which faction you choose to support, better companions (they actually have their own backstories, quests, and perks that they gain for doing their quests while FO3 companions have neither) and is more true to the feel of the classic Fallout games. New Vegas also has the "A World of Pain" mod, which will easily double your playtime even if you install no other mods.

FO3 has a more post apocalyptic feel since you're wandering around the ruins of DC and the wasteland surrounding it, some of the companions are more amusing (RL3's combat lines), better DLC, and some of the FO3 mods like Phalanx and Mothership Zeta Crew are just THAT awesome. Also, Threedog is a hell of a lot better than Mr. New Vegas as a radio host.

Basically they're both good games and you should get them both if you can, but if it's down to one or the other because of money then it's pretty much down to whether you'd rather spend more time wandering the destroyed ruins of a city with only one real way to complete the storyline (FO3), or wandering mostly desert areas but with multiple storyline branches to choose from and several different endings (NV).

But really I'd suggest watching some gameplay videos first.

I run Fallout 3 in Win7 Ultimate 64x with no problems at all.
The atmosphere is diferent as someone say, as a vet from the saga i found fallout 3 more similar to the originals, but is true that feel more like a FPS with RPG elements but the same happen to me with new vegas, also the dlc from fallout 3 are better than new vegas (Dead Money is really boring -.-! even when you play with the best goodwild). Companions in NV are more interesting and more rich plot contribution.

In before Hilary Clinton links this thing here

nv if you like fun

If you have to pick between the two, go for New Vegas. But Fallout 3 works fine on Windows 7- I've had it installed on three different PCs, all running Windows 7, and I've had no problems or performance hits.

I hated Fallout 3, loved New Vegas.

New Vegas undeniably has the better story, but I have to admit I got really bored of the setting. The Mojave was an incredibly uninteresting place to me. Someone told me the that the total area of the Mojave in the New Vegas was larger than Washington in 3, but it didn't feel like it. Also, since I didn't play the Hardcore Survival mode, I ended up not even using the extra stuff NV added (ammo creating and cooking stuff).

fallout3 is much better

FALLOUT 3, it was so much fun when i played it sooo many years ago, to this day it is my favorite game ever (well fallout 3 and The world ends with you tie in the first place) fallout new vegas it wasnt the same for me, i know that everybody says, fallout nv has better history, better gamplay etc, but for me fallout 3 was much more fun than new vegas, i have literally more than 10 gb of saves and 150+ hours of gamplay, but NV i just finished it and various side quest it wasnt the same, but it is great too!

Save yourself the trouble & just get them both, you will eventually anyways. Fallout 3 works fine on 8.1

Fallout NV is much more fun than Fallout 3...i played both and i liked the style of NV more.

This video runs down all the Fallout games. The second half is about FO3 and NV. I would give it a watch because he spells out just how the two games differ. There are some NV spoilers. So if you don't want to watch it, I can sum it up for you. Fallout 3 is The Elder Scrolls with guns. The driving focus here is the player making their own fun while following a thinly veiled plot. Where NV is a better modern interpretation of the original FO games. The driving focus is the story and giving the player choices that changes what you can and cannot while proceeding forward in the game.

Its super funny because New Vegas has TONS more content, better story lines, better factions, better lore, better pretty much everything and some prefer 3 because of the "Atmosphere" which confuses me because it felt dull compared to New Vegas, not sure how Bethesda made it dull while Obsidian made a DESERT more fun but yeah...it is a better world, less restrictive feeling, Fallout 3 as fun as it was(Not a bad game, NV just shits all over it) felt like a amusment park, NV felt like a real world.

Also the karma system in 3 is TOOOOOO black and white.

New Vegas obviously

I dunno, both are good with their own flaws and advantages. As many people pointed out, F3 has a more apocalyptic feel and better radio host and i didn't like the brownish feel of New Vegas although that one is more polished in almost every way compared to F3. Also i liked the dlc's more in F3 but that's just probably cause i didn't like Dead Money very much eventhough you get a sweet ass Holorifle after completing it which i pretty much used for the rest of the game (not to mention a crapload of gold bars as well after completing it).

I'll probably replay F3 again if they ever decide to bring steamworks to it

Or read the hundreds of existing threads with the exact same question on the internet

Save yourself the hassle and buy both. You'll end up trying both games anyway.

Fallout 3 is my personal favorite, it's dark, brutal unforgiving and truly a wasteland where you need to survive. You're more of a "lonely" wanderer detached from society only helping them if you choose to. It has a more Stalker/Metro 2033 -like feel to it, seeing all those burnt-out houses and climbing through mountains of ruble makes you feel you're living on the ruins of a destroyed civilization. It can be truly depressing at times.

In the other hand Fallout New Vegas is a bit more neutral setting-wise (probably even a bit more sarcastic, uplifting), there's a western theme going on and you inevitably end up meddling in the affairs of various groups. The looks and graphics of FO3 are way better than FNV (except New Vegas it rocks). FNV also improved a few aspects of the game, but those can be added to FO3 with mods already.

Both games have some strong DLC's so I'd get the Ultimate/GOTY edition. The Pitt is my favorite DLC for FO3 and Dead Money for FNV.

I have both, but Fallout 3 is my favorite. I don't like F:NV at all, its buggy and the story is boring imho.

fallout 3 have better story in my opinion :)

Very easy choice, Story=F3, gameplay=FNV.
The story in F3 is much better in my opinion, and in NV they polished a lot of things + more weapons and stuff (just the vanilla game, if u are getting mods this could change)

Fallout 2, next question!

both very cool, fallout 3 has more missions and dlc's, and fallout NV has cooler soundtrack and stylish theme of destroyed Vegas

p.s. played both on windows 7 works, well

I played Fallout 3 on Vista and it's working well.

From what I heard a lot of people say NV has better story. I've never personally played it, but I quite enjoyed 3, and it has a bigger landscape to explore, though I feel that the main quest is too short.

Fallout 3: More story (more boring than NV, but you will appreciate the changes NV makes if you play 3 first) Fallout NV: More gameplay (Very fun, but lacks the atmosphere Fallout 3 had)

Fallout NV cause it actually works.

Fallout 3 is very buggy, unstable and crashes a lot even with patches (and community patches).