Smooth should move more air, and an airfoil shape should move it more efficiently. Smooth should also have less drag in most cases.

A rough surface will create more turbulance which (theoretically) will reduce the effectiveness of the wing/blade.

I think that the change from cast alloy to molded plastic was simply an economic decision. The same reason that the mirror bracket was a magnesium-alloy in the early 124s, and zink in the later 124s.

__________________

Gone to the dark side

- Jeff