QUESTION: What is the purpose of discussing the comparative superiority among sūtras, which were all preached by one Buddha?

ANSWER: It is preached in the Lotus Sūtra, fascicle 7 (Chapter 23, “The Previous Life of Medicine King Bodhisattva”), “He who upholds this sūtra is foremost among all living beings just as this sūtra is foremost among all the sūtras.” This chapter of the Lotus Sūtra also enumerates ten similes that expound the Lotus Sūtra as supreme among all sūtras which have already been preached, are now being preached, and will be preached (i-kon-tō). The eighth of the ten similes is the one just cited above. In short, the true intent of the Buddha in preaching this sūtra is not to show the comparative superiority of various sūtras but to preach that the practicers of the Lotus Sūtra are foremost among all the people. The practicers of expedient sūtras such as the Great Sun Buddha Sūtra are like various mountains, stars, rivers, and the people whereas the practicers of the Lotus Sūtra are like Mt. Sumeru, the sun and the moon, a great ocean, and the great king.

Ōta-dono-gari Gosho, A Letter to Lord Ōta, Writings of Nichiren Shōnin, Doctrine 3, Pages 200-201.