Hit the nail on the head, sorry for the misconception should be like. A bigger surface would have a more smoother airflow, if it moved at 30 degrees the transition of air from one direction to the other would be smoother and less dramatic than 30 degrees of movemt on a smaller surface.

So there would be less air getting thrown off on the big surface is you get what I mean at extreme throws, less seperation.

What you two guys have pointed out is correct, I forgot that a large surface when deflected would have more area exposed to the propwash.

And the most important factor, big control surfaces make you look cool. "Look mine are bigger than yours"