It would seem that religious people are more stupid than atheists.
I'm both a religious person and an atheist, and I dislike the never-ending opposition of the two on these forums. It should not be assumed that all religion is either theistic or dogmatic. For that matter, it should not be assumed that all theists are religious. There are plenty of people who, if asked, would say they believe in some god or other, but who give that god no more thought in their daily lives than I give to Millard Fillmore.
I would not even say that religious people who adhere to dogmatic systems of religion are necessarily more stupid than atheists. You can easily find on these very forums people who believe the most remarkable and unlikely religious teachings but are demonstrably more intelligent than some of the atheists here.
I do think that intelligent people are more likely to become atheists than stupid people, both because they are more likely to question religious teaching and because they are less likely to be satisfied with religious answers. Various studies and surveys do tend to support the idea that intelligent and/or educated people are more likely to be atheists.
I think there's a more important distinction, though, and that is between ways of being religious. To choose two well-known examples here, look at Katzpur and Angellous. Both are very religious people, and both believe things that I, personally, consider to be very unlikely, but they are both intelligent and thoughtful people. As an atheist and a non-dogmatic Buddhist (and as a fairly intelligent person), I think I can more easily find common ground with them than I can with a stupid and thoughtless atheist, even though the atheist shares my views about gods.
Likewise, I think they can more easily find common ground both with thoughtful atheists and with thoughtful theists who believe things contrary to their own beliefs than they can with stupid and thoughtless adherents of their own religions. Katzpur is as faithful a Mormon as you'll find anywhere, but her views are often at odds with those of her more fundamentalist-minded brethren. And my parents are Christians like Nathan, but they would consider him so "liberal" as to find the distinction between him and an atheist merely academic.
In my view, it is not religion that is the enemy, but fundamentalism, stupidity, and intolerance.