The question of what is more important for the human birth and death of Jesus Christ, is not correct.
First of all, it is necessary to talk not only about the importance of the events of the New Testament to mankind, but most of all, the purpose of the New Testament historical events from the life of Christ.
The very moment of the Incarnation is a necessity forthe salvation of all people, a man of reconciliation and God's deliverance from the power of the grave (which got all the people until the death of the Savior on the cross). Christ incarnated to give the opportunity to regain the opportunity to be with God after death.
It is not necessary to talk separately about the birth of Christ andhis death. All this is aimed at a single action - the salvation of man. Although, in the orthodox dogmatic textbooks can find information about that man's salvation through the death on the cross was the second Person of the Holy Trinity. This is true - through the death of God, man acquires the possibility of eternal life with God after death. However, if there would be the fact of birth (the Incarnation of Christ), we would not have talked about the sacrifice of the Cross.
Now we can say about the importance ofIncarnation (birth) of Jesus Christ on the other side. God himself takes up the human body, in a single incarnation of the second Person of the Trinity voipostaziruetsya human nature. The human being is consecrated, it becomes fertile. It is also necessary to take into account when we talk about the birth of Christ. One of the ancient saints of the Christian Church said that God became man, so that man might become God. Of course, a person can not have the divine nature (being), but he can shew to "God" by grace.