Ryuken vs. Souther

The original Hokuto Shinken Successor vs. The master of Nanto Ho'oh Ken. Who wins?

Souther should unless Ryuken knows his secret, even then, knowing is only half of the battle. Is this Ryuken in his prime or old man Ryuken from the manga/anime?

Old man Ryuken without him needing to worry about dying on the spot while fighting.

Probably Souther.

Souther. He blitzed Kinship with pure speed.