It's swordsman versus ninja in an all out 1-on-1 free for all! First, let's get the lowdown on each of our combatants.
Pros- Zoro has one extra sword more than Leo. Zoro also has slightly more experience in the art of sword fighting.
Cons- Zoro's abilities and skills are greatly reduced when he is using only 1 or even just 2 swords. Zoro also tends to lose focus and become angry when the fight is not going in his favor.
Pros- Leo is not a swordsman, he is a ninja. Therefore, he has supreme skills in the martial arts in addition to his skills with the sword. Leo can defend himself very well even when he is unarmed. Leo can stay focused even in the heat of a seemingly hopeless battle. Leo's shell also provides a natural armor for his back and chest.
Cons- Leo is not as skilled with sword wielding as Zoro. As long as Zoro has all 3 of his swords, Leo is at a disadvantage.
My predicted winner: Leonardo
Zoro simply relies too much on his swords to win his battles. Leo relies on his own abilites of his own mind and body. Also, being a ninja, Leo would be able to use stealth in addition to speed and endurance. The likelyhood of Leo being able to knock away one of Zoro's swords is very high. That's why Leo is the better fighter IMO.
((Sorry RoboBlue, but I just couldn't figure out how to make a decent fanfic out of this.))