Didn't you do this one before?
I'm going with Yoda, but I think Caedus would win in the end.
Edit: In this fight, the only thing Yoda has going for him is his size and speed. Could be a game changer, but in reality it will only close the gap slightly. I think Caedus would win eventually.
It is funny how people try and measure just a person's raw power and not experience. Yoda has over 900 years of experience to bring to the table. Yoda might talk him into giving up the dark side and returning to the light.