Okay... I don't know if you forgot to mention power savings or increased speed per watt but -
If you travel at 25mph with *any* equipment, you're going to have the same time taken over 40km...

But in regards to power, the higher the speed (and therefore power), more aerodynamic equipment will provide increased savings of power at a higher speed.

Unless the route is hilly, aero stuff is more efficient than light equipment (unless it's full of traffic lights).