Well, it depends what you want out of life. Truth or illusion - I am tempted to say.
Many argue that without God and without belief in God, the existence of the world is somehow mysterious. What is paradoxical about this claim is that many people who argue thus also say that God is mysterious. So, on this view, one mystery is replaced by another. Is that progress?
Many argue that without belief in God, there would be no sense of right and wrong, of what is morally good and bad. That is a frightening claim. Are such believers really saying that if they lacked belief in God, if God did not exist, then they would think it was perfectly all right to rape and pillage, torture and kill for the sheer fun of it? - that it would be okay for me to give well-argued essays low marks and poor essays high marks? If they are not saying that, then it shows they do not depend on belief in God for a sense of right and wrong. If they are saying that rape and pillage etc would be fine, if God does not exist or there is no godly belief, well it is best to steer clear of such people...
For further links to such thoughts, try humanism.