Foundry Revan displays none of the tactical aptitude or unrelenting skill in combat we know Mandalorian Revan was in possession of. In fact, Foundry Revan doesn't seem all that competent of an adversary in general (no doubt still recovering from being Vitiate's tv dinner for 300 years). Thus, I'm inclined to believe Manda Revan nudges a victory by after a long and hard fight due to superior discipline.