Kakashi due to his observation skills. It won't take him long to realise that Hidan can't die.
Then he will probably come to the conclusion that the best way to beat an overconfident stand still and take it type, immortal guy, would be to blast him into another dimension.
Hidan is not familiar with Ocular skills and likes to take beatings, then laugh.
Likely he will stand there and take the Kamui and simply be warped into Disney Land or wherever they go.
As far as I've seem Hidan doesn't bother about dodging too much and instead uses the opponents attack as his oppertunity to take a few slashes but give just one back himself, thus gaining the blood for his tech.
If it came to an exchange of blows, Kakashi, with the Shaningan/MS would be able to see his moves and dodge. Likely though not cert.
As long as Kakashi doesn't get hit, He will warp Hidan away. Easy.
Just a matter of how long till Kakashi thinks of it.