Board Thread:Versus Debates/@comment-1018594-20150717101621/@comment-5407586-20150717115714

Shisui's genjutsu prowess made him the strongest genjutsu user of the Uchiha clan, a clan that possessed the Sharingan. While Sasuke was able to "break" Itachi's Tsukuyomi, I don't think he (or anyone else for the matter) could break the Kotoamatsukami.

Taijutsu-wise, I'd give it to Shisui in speed, though Sasuke isn't slow at all, and might be able to even exchange blows with the opponent for some time.

Ninjutsu-wise, Shisui and Sasuke should be tied in normal Fire Release, but Sasuke's Amaterasu and Blaze Release should give him the upper hand. In Lightning Release, Sasuke should win with Chidori and its derived techniques, but Shisui has Wind Release, which is superior to Lightning Release. With the Susanoo, both Sasuke and Shisui are proficient in mid-to-long range fighting (bow and arrow & chakra needles), so they'd be tied.

Shisui wins.