More efficient: All believe, or No belief

Today I was thinking about Utopia and other scnearios that the world could encounter far along down the road of evolution and a weird question came onto me. What would honestly be more effective for our evolution as a race/species/world..etc. Would it be better for every single person on the face of this Earth to share the same religion, wheather it be Christian, Muslim, Buddhist, etc..OR Would it be better to have an entire society of people, every single man, woman, and child on the face of this earth to be Non-believers.

I guess really there isn't much of a difference rather than one potential group all beleiving that we are here on this Earth for some reason, there is a higher power at work. And the other group would all believe that we have no reason for living on this Earth, and we are just a very small chance that we have evolved to this point. It's a very vast subject to try and deter in my head, but honestly I would have to say as believers our morals would be more in tact if all humans shared the same religion and beliefs, but we would advance much faster if we were all non-believers (ex: stem cell research, abortion/population control/human harvesting for energy)