I like them all. I did happen to like Tavion a lot too. Desann? He sucked! The reason I dislike JO so much is the lack of a good character comparing it to the greatness of DF2.
I'd go with Yun. I liked his look, his saber color/ hilt, and his redemption. It's done better in the book. His last words were something like, "Can you see the light, Sariss? How bright is it?" His master/ apprentice relationship with her was done well and hardly evident in the game.
As said, I liked them all. Jerec was so evil. He's like Maul and Dooku put together. That sinister monster and a gentleman villain. Sariss was probably my least favorite in game but as said, she earns points in the books. Maw is a floating torso of pure anger. What's not to like? Gorc and Pic had a cool concept but needed more characterization in game and I never read the book that they fight Kyle in. Still, a mutated Gamorrean and Kowakian Monkey Lizard fighting as a team is pure genius!
"The Force is strong with Katarn...." - Darth Vader, Star Wars: Dark Forces