It is better to convert one person to Nichiren's Lotus Sutra Buddhism than ten million to the Soka Gakkai.

“Some people criticize me, saying, ‘Nichiren does not understand the capacities of the people of the time, but goes around preaching in a harsh manner—that is why he meets with difficulties.’ Other people say, ‘The practices described in the “Encouraging Devotion” chapter are for bodhisattvas who are far advanced in practice; [Nichiren ought to follow the practices of] the “Peaceful Practices” chapter, yet he fails to do so.’ Others say, ‘I, too, know the Lotus Sutra is supreme, but I say nothing about it.’ Still others complain that I give all my attention to doctrinal teachings. I am well aware of all these criticisms against me. But I recall the case of Pien Ho, who had his legs cut off at the knee, and of Kiyomaro (Pure Man), who was dubbed Kegaremaro (Filthy Man) and almost put to death. All the people of the time laughed at them with scorn, but unlike those two men, those who laughed left no good name behind them. And all the people who level unjust criticisms at me will meet with a similar fate. The ‘Encouraging Devotion’ chapter says, ‘There will be many ignorant people who will curse and speak ill of us.’ I observe my own situation in this passage. Why should it not apply to all of you as well? ‘They will attack us with swords and staves,’ the passage continues. I have experienced this passage from the sutra with my own body. Why do you, my disciples, not do likewise?” (pg. 209)

The SGI teach “Lesser doctrines”: Value creationism; human revolution; shoju in the degenerate age; mentor-disciple as the prime point of the Lotus Sutra; the inequality of those who chant the Daimoku; the purpose of the Juryo-hon is to smash the Hoben-pon and the purpose of Daimoku is to smash the Juryo-hon; Nichiren is the True Buddha; Namu Myoho renge kyo is the True Buddha; Namu Myoho renge kyo is incorrect, Nam Myoho renge kyo is correct; the Lotus Sutra has lost it’s efficacy in Mappo; the common man can not understand the Lotus Sutra or Gosho in Mappo without Sensei's guidance; prayers to repay one’s debt of gratitude to the Three Presidents, not the debt owed to Shakyamuni Buddha; the Nichikan Gohonzon; personal guidance; the list goes on and on. The concept, “innumerable meanings derive from one Law”, does not mean any base or mistaken concept is Buddhism.

The One Vehicle is Myoho renge kyo:

“Thus it was that the eight-year-old dragon girl was able to come out of the vast sea and in an instant give proof of the power of this sutra, and Superior Practices, a bodhisattva of the essential teaching, emerged from beneath the great earth and thereby demonstrated the unfathomably long life span of the Buddha. This is the king of sutras, defying description in words, the wonderful Law that is beyond the mind’s power to comprehend.” (Embracing the Lotus Sutra)

Nichiren does indeed teach, “Never seek this Gohonzon outside yourself. The Gohonzon exists only within the mortal flesh of us ordinary people who embrace the Lotus Sutra and chant Namu-myoho-renge-kyo.” But he also teaches that the mandala Gohonzon (Original Eternal Buddha Shakyamuni) is the teacher of all Buddhas throughout the Three Existences:

“If it is not the proper Object of Worship (Gohonzon), even though there be no falsehood [even if the practitioner is sincere] it will not form the seed [of Buddhahood]. The Daimoku of the Hommon [Doctrine of the Original of the Lotus Sutra] is the seed of Buddhahood. This is because the Eternal Shakyamuni of the Honmon has put his Causal Practices (his myriad practices that lead to enlightenment) and his Virtues of the Effect (the merits of the effect, which is Buddhahood) into the seven characters of Namu Myo Ho Renge Kyo.” -- The True Object of Worship

and

“If one doubts the strength of the Buddha when he says, “I am the only person who can rescue and protect others”; if one is suspicious of the rope held out by the Lotus Sutra when its teachings declare that one can “gain entrance through faith alone”; if one fails to chant the Mystic Law which guarantees that “such a person assuredly and without doubt [will attain the Buddha way],” then the Buddha’s power cannot reach one, and it will be impossible to scale the embankment of enlightenment.” (Embracing the Lotus Sutra)

and again, it is not enough merely to believe in and chant the Mystic Law:

“Only when one understands all this clearly and believes in it can the Law manifest its power and the Buddhas and bodhisattvas bring benefit to the people. To illustrate, in kindling a fire, three things are needed: a good piece of steel, a good flint, and good tinder. The same is true of prayer. Three things are required— a good teacher, a good believer, and a good teaching— before prayers can be effective and disasters banished from the land.

A good teacher is a priest who is free from any fault in secular affairs, who never fawns upon others even in the slightest, who desires and is satisfied with little, and who is compassionate; a priest who reads and upholds the Lotus Sutra precisely as it teaches and also encourages and leads others to embrace it. Such a priest the Buddha has praised among all priests as the finest teacher of the Law.

A good believer is one who does not depend upon persons of eminence or despise those of humble station; who does not rely on the backing of superiors or look down on inferiors; who, not relying upon the opinions of others, upholds the Lotus Sutra among all the sutras. Such a person the Buddha has called the best of all people.

As for a good teaching, the Buddha has told us that this sutra, the Lotus, represents the foremost among all doctrines. Among all the sutras the Buddha “has preached,” among those he “now preaches,” and among those he “will preach,” this sutra is designated as foremost, and therefore it is a good teaching.” -- How Those Initially Aspiring to the Way Can Attain Buddhahood 

Being a good believer is insufficient

As far as the “great good” of planting seeds, the SGI seeds are damaged because their Object of Worship is damaged [mistaken]. The beautiful saplings [SGI new members], as they mature, grow into crooked Taisekaji trees. It is better to convert one person to Nichiren's Lotus Sutra Buddhism than ten million to the Soka Gakkai.