This question is like asking, which fruit is better, an apple or an orange? Which faith you choose to believe in and practice is an individual choice. There are many similarities and many differences between Islam and Christianity and every person has to decide for themselves which one is best for them. Some of the similarities include both Islam and Christianity believe in only one god.
The difference is Islam’s God is called Allah and Christianity’s god is a triune or trinity called God or Yahweh. Islam believes man was created by Allah as sinless. Christians believe man was created in God's image and is sinful by nature. Only you can decide which faith is better, by studying each religion’s beliefs and talking to an Islamic religious leader or a priest.