Darth Venamis vs. Ulic Qel Droma

The man who fought Plagueis vs. Turncoat Sith lord

Force, sabers, all out

Both primarily duelists. I'll go with Ulic.

Could go either way. Ulic has outran/outmaneuvered Mandalore's blaster bolts and generated multiple after images and blurs. He's likely just as fast.

Saber ability might go to Venamis. I'm not sure actually, if Venamis wins I wouldn't be surprised. Fighting Plagueis is probably a better feat than merely stalemating Exar

But with a style specifically designed from the ground up to trump Plagueis's. That's got to count for at least a tier in duel ability.