Which is better?

I enjoyed Fallout 3 just sightly more than New Vagas but both really really good games!.

Fallout 3 captures a breathtaking atmosphere, but New Vegas creates a more innovative role playing experience. I liked the Mojave better the Captial Wasteland because the Mojave is much more diverse. One moment you could walking through an untouched town,
the next a devasted hell hole. There's also more side quests in NV than 3, some of them are rather pointless. With that said, 3 had better side quests.

Get both if you are wondering. Both are worth it.

I like fallout 3 better. There is just a lot more to do, especially with huge DLC like point lookout and broken steel. Also fallout 3 is way larger with more locations. In fallout NV you can find locations with no entrance(boarded up doors), and that is
just pathetic. In FO3, pretty much any building you find on the map can be entered. Both are good games though. FONV has it's perks too. The game has SO MANY WEAPONS. It is insane how many it has compared to fo3. Not only way more weapons, but way more ammo
types like ammo piercing. Also FONV has a lot more monsters. In 3 there is 1 type of death claw, in NV there is like 5+.

I agree with most. Fallout 3 seemed deeper in the story. Fallout NV while it is a great game, felt as if the story could've went on after the ending.

Also; Fallout 3 you are able to continue after the main end quest, in NV you are not.

No bobbleheads, but there implants you can buy instead. You can get one per base endurance (Intense Training boosts count but the implant does not). There is one implant for each SPECIAL plus one that boosts your DT and one that allows you to regenerate.
It is nice to not have to go hunting for these, though they will eat up a fair chunk of cash and you need to be aware of the endurance requirements when creating your character.