It's difficult to say. JP is the MVP of Dream Theater overall, he is the source and the engine. Awake was JLB's best performance as a singer and one of the best performances by any singer on any prog metal album.
Still, I voted for Kevin Moore because a) you guys are haters, all of you!
b) a lot of ink has been spilled about whether DT is better with three heads strong in the game or just two. From the beginning with MP, JP and KM really battling it out for how the songs were going to go, then with MP and JP steering the ship until they allowed Rudess to rock the boat more, and the JP/JR show since MP left. They made good and bad albums in all configurations - but my favorite albums come from the first one. And a large part of that is thanks to KM's unique viewpoint, specific taste, lyrical talents, and artistic trajectory.