I know Yoda was prequal era. This is very, very obvious. What I am saying is Yoda at a younger age MIGHT be able to beat Jacen. (I hate the name Caedus.) This is one of those "what if" fights. As powerful as Jacen was I am not 100% sure he could handle a younger Yoda. Maybe he could, who knows? I still think it would be a draw. I honestly cannot say who would win.
I don't think age is really a factor. Sure Yoda would be more "spry" at a younger age, but I don't think it would change much. Remember that Dooku beat Anakin and Obi-Wan when he was "aged". And then he beat Obi-Wan during his final duel, while being attacked by Anakin. Age isn't a big factor. Yoda's mobility? Yes. Yoda's biggest strength in this fight, besides his strength in the Force, is his speed and size. But Caedus would win in the end. Not easily, but he would.