Please be honest and post why. There are, what, 4 DLCs? Never played any. Which is the best IYO?

Three have been released, Dead Money, Honest Hearts and Old World Blues.

I think Dead Money is best because of the story, the atmosphere, the gear, the perks, the survival aspect, the new challenges it brings, the characters, the quest design, the choices, the backstory and the new home.

Honest Hearts and Old World Blues on the other hand are just two sandbox maps with fetch quests that desperately try to provide a good story but fail horribly.
They're both way too linear IMO.

OWB it has the most exploration and some great weapons and a good funny-ass story.

the one where they're living on mars and theres this kid who they think is autistic but is actually living in a different form of time where he sees things that are going to happen far in the future but his physical body is still in the present. so arnie kott tries to take advantage of this ability for his own motives....wait that was martian time-slip.

Old World Blues since it's the only DLC with true Fallout spirit: An abandoned pre-war facility with gruesome experiments, black humor, exploration and emphasis on dialogue.

Honest Hearts a close second mostly because of Joshua Graham. He is one of my favorite NPCs in the game.

Honest Hearts, because of the scenery, the new weapons, Joshua Graham, and for being combat-heavy.

They're all good. Old World Blues is my favorite, and most other people's. Honest Hearts is pretty good, though annoying at times. The tommy gun makes up for that though. Dead Money is also good, but most people complain about it because it proved difficult. It's all a matter of opinion. If you want the best weapons, go Honest Hearts. Best story, Dead Money. Best overall, Old World Blues.