What is the most successful argument that Melville makes in "The Advocate"?

Given that Melville makes nearly a dozen arguments in favor of whaling in the chapter "The Advocate," the choice of the most successful argument is somewhat subjective. Many of Ishmael's arguments reflect a mid-nineteenth-century (and even modern) concern that one's occupation is considered an honorable pursuit. While conceding that whaling isn't respected as a profession and that no whaler could use his profession on a calling card in high society, Ishmael presses on to advocate for the whaling trade.
For a modern observer assessing the practical benefits to society of the nineteenth-century whale trade, Ishmael's argument about whale oil lighting the lamps and candles of much of the world stands out. While many of his other arguments sound like stretches, and many are downright comical (as Melville intended), the fact that whale oil lighted much of the world and that whaling was a large and profitable industry until the advent of kerosene cannot be denied. This underscores the real importance of whaling to the economy of the nineteenth century.