Question on wind deflector

I am no fan on the use of the wind deflector (ie. the plastic black colour deflector that mounts on the front of the hood). Some of their ad materials claim it deflects the road debris like small gravels and sands away from the front hood and thus reduce stone chip damage. Some even say it improves fuel economy by changing the areodynamic of the car.
I don't agree to such claims because if it deflects the flyer debris, then the debris will be landing on the windshield instead of the front hood. Samll sands will also sandblast the windshield. The cost of damage or replacement may even be higher than touching up the paint chips. Secondly, I don't think any after-market add-on can improve the fuel economy than the original manufacturer design of the vehicle dynamics.
What do you think about this?