I'm going to say Guts because he has a cannon on his arm which would easily blow Kenshin away.
But sword/sword I'd say Kenshin would win since he seems to be a better swordsmen. Though Gut's raw brute strength combined with his massive claymore might be enough to tip the balance in his favor. I really don't know.
Oh, and Berserk is spelled with a S. I thought it was spelled with a Z for a long time as well.