There seems to be some confusion for the best Kitetsu sword. According to wikia, Shoudai Kitetsu is Saijō Ō Wazamono Grade Sword while Nidai Kitetsu is Ō Wazamono Grade Sword. In the manga Chapter 97 page 13, Tashigi said Nidai is better than Shoudai. It can only be speculated why Tashigi said that or is the result of a bad translation. Cant wait for the debut of the swords!