I approach this problem from a philosophical and a practical sense and both lead me to be an atheist.
From a philosophical view, I've chosen to live my life to not believe in something unless I am able to test it myself. This does not mean I *do* test everything myself (some things I do), but having the option makes me comfortable. Can I test Quantum Mechanics? Well, yes. I've personally derived many of the expressions and I've seen results in clean rooms. Can I test that jesus rose from the grave? No, nor are there reliable sources that says he did.
From a practical view, there are two problems. First, I have no idea *which* religion to believe. There are an infinite number that could be right. Statistically, my chance of picking the correct one is 0. So, to me, it seems better to live my life as if there is no God. If I'm right, I didn't waste every Sunday morning. If I'm wrong, I can beg for forgiveness at the entrance to Valhalla, or on the shore of the River Styx. Also, I simply *cannot* believe in a god that would damn me to hell for not using the brain he gave me, so I'm actually incapable of sincerely believing in a god.
Either way you look at it, atheism makes more sense.