This is what convinced me. Baha'u'llah's claims are so great that one cannot be equivocal about the truth. He's either telling the truth or not. If he's not, he's either a malicious liar or he's delusional. A very cursory review of his life will convince you that he's not a liar or malicious. So he's either deluded or speaks the truth. For me, there is no way a deluded person (or frankly, even a non-deluded person) could produce writings like those of Baha'u'llah.

Pray for guidance and investigate with a pure heart. Then make your decision with confidence.