The question would be more interesting if it was "Who, besides Montgomery Scott, was the best Chief Engineer?"
Then we might have a conversation.
Then that would be O'Brien
Kept an Alien (to him) Starbase running
Fixed Design Flaws or at least had a significant had in fixing those flaws on the Defiant Class
Had to oversee repairs of ships during the Dominion War that were at DSN for repair
Became Professor of Engineering at Starfleet Academy