I would confront neither. I would gather my things and leave -- without all the drama. We're not cavemen who grunt anymore. We're grown people who can speak words to express what's on our minds. A cheater cheats when they're too lazy to express feelings of boredom in a relationship, when they're too childish to control their sexual urges, and/or they're so full of themselves that they think they can have anyone they want. Why waste breath, reasoning and time on someone who didn't do the same? Cheating on someone is insulting, disrespectful and pathetic and I would advise any victim of a dishonest partner to get far, far away immediately.