Battle! Psycho Mantis vs. Seymour

Any abilities that he had access to in the game he has access to here, unless the judges call foul on any of his abilities.

I say Mantis. Why? He can read minds. There's not a single thing Seymour could do to outmaneuver Mantis' mental probes. He would anticipate all of Seymour's attacks, and would counter them accordingly.