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.
Guts has a cannon and a crossbow gun thingy on his metal arm, A massive sword almost the same size as him that only he seems able to lift with his overwelming strenght, He does what ever he can to win whilst ignoring the pain from his wounds and dodging multiple attacks and is quite skilled with a sword. He's fought 100 people at once and won, With one swing of his sword he can slash through 10 men, He's only been defeated once and Just imagine if he wore lighter armour and carried a lighter sword, it would increase his speed greatly therefore i think that he would win.