I would guess that atheists are better. Mainly because atheists are concerned with reality while theists are, well, not. Theists, by nature of their belief in a higher power, are probably much more likely to believe in silly superstitions and "luck." Of course I have no evidence whatsoever to back up anything I have said. Just kind of the way it would seem to be.

And yes, in case it wasn't obvious, I am an atheist.