Why does Pi tell two different stories of what happened to him?

Part 3 of Life of Pi revisits and reemphasizes themes raised earlier in the novel, as well as complicating and redefining them and the story itself. With the exceptions of the author’s chapters scattered throughout the novel, Part 3 is the first significant portion of the text that departs from Pi’s point of view to tell his story. This is especially significant, because Pi has claimed that his story is over; the author’s choice to continue it is in a way a departure from Pi’s presentation of, and thus control of, his story.

This idea of narrative control is crucial. Pi tells Mr. Okamoto and Mr. Chiba that everything in life is inherently a story - even facts, because they are being perceived by someone, and thus can never be truly objective. Yet in the mens' unwillingness to believe Pi's story, they weaken his control over it. Even faced with evidence—the floating bananas, the meerkat bones—they stand firm in their disbelief.

In response, Pi tells another story, one which should be more believable to them. In being forced to do so, he is in essence losing his control as storyteller - for the mens' dislike of zoo animals being involved must define how he tells the story.

Pi’s second story is, seemingly, more realistic, as well as significantly more tragic and horrifying. In both stories, he survives a long and terrible ordeal, but in the second, he seems to contains both his own, rational self, and the ferocious, wild, and very dangerous Richard Parker. Even if this is not the “true” story, the possibility of such a division of Pi’s personality is made clear by his doing so here—throughout his ordeal, we see his need to survive slowly overpowering his rational (vegetarian) self.

Yet while the second telling of the story may cast doubt for the reader on the first story, it is not meant to do so for more than a moment. Even the highly skeptical Mr. Okamoto and Mr. Chiba in the end choose to believe the first - the better story - because Pi tells them that they may. Neither story affects their investigation, so there is no reason not to take the less tragic and more "enjoyable" story as the true story. And this is how Pi finally defines his belief in God, and why Mr. Adirubasamy tells the author that this story will make him believe in God. Why not believe in a fundamentally benevolent universe?