Shouldn't Jedi be better duelists than Sith?
If you consider what the Sith and Jedi rely on.
The Sith are actually permitted to use the force offensively. However the Jedi cannot use the force offensively, so how would they survive and defend the galaxy against the Sith Lords? The only real advantage I see a Jedi Knight would have against a Sith Lord would be superiour dueling skills.