The Celestialsapien wins by virtue of it universe busting and recreating universes with no effort, while Q has not shown feats on this scale.
That said, Celestialsapiens are not omnipotent. Source: Word of God statement that says there are beings above the Celestialsapiens in Ben 10. And unless that writer was Lionel Suggs, I'm afraid there's not anything beyond omnipotence.