In each of the three religions he finds something he likes or needs.
He is attracted to Christianity because of the story and because of its existence in the present. Pi says, "The first thing that drew me in was disbelief...What a downright weird story." But it is the story and its simplicity that drew him in. He battles with himself and with Father Martin for understanding. At the end, he can't get the story of Jesus out of his head. He concludes with "Christianity stretches back through the ages, but in essence it exists only at one time: now.
He is attracted to Islam by its rituals and its spirit. Pi says, "It is a beautiful religion of brotherhood and devotion." It is the way of devotion, the daily prayer and the physicality of it that attracts Pi.
Hinduism represents his home. He grew up with the smells and colors of Hinduism and its stories. Pi also tells the reader that, "the universe makes sense to me through Hindi eyes." He understands his world through his upbringing and through Hinduism however, he is not exclusive about this. In the other two religions, he finds something to love.
We see that Pi is attracted to all three for distinct reasons, all of which help him survive his ordeal on the boat. He sums it up himself beautifully, "Hindus, in their capacity for love are indeed hairless Christians, just as Muslims, in the way they see God in everything, are bearded Hindus, and Christians, in their devotion to God, are hat-wearing Muslims."