Wow if this link is true he Plo Koon is on Count Dooku's level but I highly doubt that. http://hometown.aol.com/strahd54/plokooncut.html
I think Plo could beat Luminara (waits to be yelled at).
Okay, seriously, though. Starwars.com has this to say of Luminara: She has incredible talents with a lightsaber (but it says her and Bariss Offee so we can't be sure if it's true or not). Years of intense training turned her body into a weapon itself, increasing the flexibility of her joints to allow her inhuman agility in combat.
Koon: well-muscled, Koon served valiantly as a general in the war on many battlefronts in the years that followed. The Force runs strongly in Plo Koon's family; he was a descendent of a long line of Jedi.As a Dorin, Koon naturally possessed highly developed extrasensory organs that supplement his already formidable Jedi attributes.Koon was more martial a Jedi than most. Kel Dor natives have a reputation for seeing moral issues in black and white, with clear distinctions between right and wrong. As such, Koon often took decisive action with little contemplation. This initiative served him well during the Stark Hyperspace Wars, when he took up the Republic banner after a great Jedi Master was killed. Koon rallied the disheartened troops to an unlikely and miraculous victory.
So Luminara has incredible saber talents and can turn her body in unusual and unexpected ways, making her even stronger.
Plo is physically strong, the Forcr runs strongly in him, he has a fighting reputition, and he made at least one great victory.
Okay, both are strong. Actually I'm not sure who'd win. But I'll say Plo just to be different.