Kororsensei might not use the sound clapping technique, Especially with both of them having no weapons.
But he has far much more experience than Saitama with Genius level intellect.
Saitama won’t be that affected by Korosensei’s Manipulation Techniques since he is a very determined person, who wouldn’t stop at anything, if his “training” is any evidence. He might also have an AP advantage here.
Still Voting Korosensei.
Korosensei has far better skill, experience and intelligence than Saitama but his AP and will power can also turn the tables but not enough to win.
Korosensei has a fear inducing aura, far greater skill and he’s an expert Assassin who’s very intelligent.
Saitama has the AP advantage but as Korosensei states in the anime dub “Those who were stronger than me I killed with Knowledge” so yeah, nothing much to stay there.