In view of the recent news of 1 out of every 4 people worldwide being Muslim, let me give some thoughts to consider (both for Muslims and for those considering the differences between Christianity and Islam):
1. One of the central issues centers on the authority and trustworthiness of the Scripture and the Koran.
When a person examines such things as the methods of receiving, preverving and propagating the truth ,along with the measure of internal consistencies vs. contraditions, the Bible proves worthy of acceptance and belief whereas the Koran and Hadith do not.
2. Another issue of consideration is the difference between the God of Christianity and the God of Islam.
The God of Christianity is one who atones and is a redeemer whereas Allah is a determinst and hater.
3. A third issue regards differences in the person of Jesus Christ. In Christianity, Jesus is the only begotten Son (Son of God) and came to reconcile man to God through the cross whereas Islam recognizes Jesus only as a man and a prophet (even one whose words cannot be trusted because the record of them is corrupt).
4. A fourth issue involves the crucifixion. In Christianity, God himself secures man's redemption by paying the cost himself through his Son and vindicated him by raising him from the death whereas in Islam man is left to secure his own salvation either by jihad or by good works (though good works may still not be sufficient and hence assurance of salvation cannot be attained or possessed).
5. A fifth issue involves the difference in the witness in that Jesus fulfills the prophecy of the Old Testament whereas Mohammed does not. In fact, Muslims claim that Jesus Christ stated Mohammed was coming, but this is not found in Scripture. The fulfillment of Christ's words are found in the Holy Spirit not in Mohammed.
6. A six issue involves differences in views of human relations. Christianity recognizes both the equality and differences in men and women (and their respective roles) while Islam does not and even fails to respect women. Additional differences are seen in marriage including the rights and consequences of it's participants.