NANIWA ( ナニワ研磨工業株式会社 / NANIWA ABRASIVE MFG. CO.,LTD.) is the name of manufacturer of both NANIWA Super Stones and NANIWA Chosera lines.
So it is a bad idea to compare NANIWA with Chosera.

Chosera stones are harder, usually faster and more versatile than Super Stones.
Super Stones are designed with intention to mimic some features of jnats that are essential for sharpening of traditional japanese hard carbon steels like Aogami, Shirogami and Kigami.
Super Stones give perfect result for such a steels. But they are unpredictable when applied to stainless steel.