Pi is an interesting kid, because he finds much to be admired in many different religions, and decides to become members of three prominent ones. This disturbs his parents, and the leaders of each individual church he attends, but Pi finds elements that are wonderful in each of them.
Pi joins the Christian faith, the Muslim faith, and the Hindu faith. In each one, he likes different aspects of it. In Christianity, it was Jesus Christ and His ultimate sacrifice that appealed to Pi. It was illogical but touching, and that selflessness really moved him. He said that it was Jesus' "humanity that I found so compelling," and after thinking about Christ and his sacrifice of self for sins for three days, he was hooked. That was the main appeal for Christianity--the love apparent in that act. His attraction to the Muslim faith was centered in its "religion of brotherhood and devotion," to its calisthenics, its open-aired temples that was open "to God, to breeze," and how it felt good to pray so often. Hinduism appealed to him because of its many sensory elements, and because of the element of Karma and a larger universe that is "aware" of all things.
Each of these religions held a special and very moving place in Pi's heart, and the bottom line was that the existence of God--in whatever form--was a great comfort and strength to him. Martel insists that is one of the functions of religion--to tell a story that provides humans with strength and comfort, as they did for Pi. I hope that helped; good luck!
Pi first follows Hinduism as both his parents, although neither practice the religion, were born into it. The boy then discovers Christianity on a trip to the tea plantations and finds that he likes the Story of Christ. The third religion Pi subscribes to is Islam which he comes to as he explores his native Pondicherry.
In each religion Pi finds comfort and hope in the story, the love, and the belief in God.