Considering my (possibly) evil twin would be an unintelligent religious nutjob who couldn't stratigically plan his way out of a wet paper bag, I'd beat him. He may be stronger then me if he is indeed my polar opposite, but if he was indeed my polar opposite his strenght wouldn't matter. He'd probably never turn his back from the spot he expected me to be in, trusting God to protect him, and therefore would never see the knife about to be jammed into his throat.