The best example of aero drag vs weight that I know of is the streamliner Honda built by Allert Jacobs:
214 mpg with DIY aerodynamic fairings on a Honda 125cc motorbike
It
gained 43% of it's original weight, and yet with the streamliner fairing (and the taller gearing that the lower drag makes possible) more than
doubles the FE of the motorcycle.
So, I say that aero drag improvements trump weight savings - by a lot.