I used to use the plastic shield, but abandoned it after a short period of time. It probably protected the toad from some stray debris, but I found it a pain in the neck to install each time, and to store when not in use (although it does fold in half).
Instead, I just installed a nice looking rock/bug shield on the front of the car's hood and some clear protective adhesive covers over the headlight lenses. The motorhome also has a full length rear mud flap. With that combination, I've gotten only some minor paint chips, mainly on the car's front rocker panel, but nothing to cause me much concern.
The KarGard II "bib" seems as though it would protect the car better than the shield and the ad says it rolls to the RV bumper "for easy storage when not in use". I don't know how much trouble it would be to use, but it looks like it might be a great improvement over the plastic shield.