Both are very interesting, but I think the anti-hero archetype often just leads to the usage of "bad boy" characters. It can be used very well, but it's usually very simplistic. The anti-villain, on the other hand, is normally a complex character with a lot of depth to their motivations.

Like Whiteflame said, the anti-hero easily gives birth to a somewhat dull bad boy type. But the possible differences are pretty varied and I've pretty much found myself enjoying most of them. While I'm interested in a good anti-villain with unique approaches on how they do things, I prefer the various anti-heroes that don't fall into all the traps a normal hero does.

I would prefer to go with this. I think I agree with Flame, in particular, plus, many anti-villians tend to be overtly interesting.

I've come to love anime anti-heroes due to the symbolism possessed by those I have come across. =)

I'm much prefer Anti-Villains myself. I'll be another to agree with Whiteflame's thinking. To me it feels like it would be so much easier for someone to make an Anti-Hero; grab a hero, add any "dark" trait(s) and hey presto you have yourself an Anti-Hero. So many are just lazy examples of just that. Anti-Villains just seem to possess a bit more 'oomph' to their character as a whole.