Okay, two things from me, and I've only looked at posts 201-here,
1.
Yes, it's different. I haven't seen a recent study, but about a decade ago, there was a study that showed that less than 1% of prison inmates were atheists. I've read a few rebuttals to this; one of the better ones being that the atheist prisoners converted while in prison after realizing their mistakes. This may be the case for some, but it ignores the problems of recidivism - for it to be logically correct, people would be atheists out of prison, convert to Christians in prison, then convert back to atheists upon release, then convert back after committing another crime, etc.
2nd: is atheism a belief system or not.
I've seen a few people argue that the lack of a belief doesn't mean it's a belief system. To this, I can agree to an extent. Because, of course, you would say "well, just because I don't believe in unicorns doesn't mean it's a belief system." Nonetheless, it overlooks a major difference - you've made a conscious effort to weigh the choices and significant arguments that two sides have.