Difference between good Christian believers and non-believers

I pondered upon this question many times. As I now know that even non-believers (those that do not attend church, not interested in religious matters and do not pray) could be in heaven with God if they are able to live a morally upright and honest life, and the environment and circumstances they are in do not encourage them to practice the faith.  So what is the advantage of being a firm believer of the Christian faith?

Now, we can compare a good Christian believer and a good non-believer. Both should have the same condition, body and soul, at birth. However, the goodness that one can attain being a Christian should normally be superior and more perfect since the model of that goodness is Jesus, who himself is superior and perfect, and the work of the Holy Spirit and the spiritual graces In the end, a good Christian has higher possibility to enter heaven, with no or shorter period of expectation in purgatory (purification of souls); while a non-believer would need a longer period to be able to reach the perfect knowledge of God and His Christ. Think of an athlete with the similar skills and conditions. The athlete who undergoes intensive training and improves his skills is in a better position to succeed than the one who does not train.