I have used both Rain-x products. The de-fogger is great. The rain-x product for exterior use I have mixed feelings about. If apply well to a clean windshield, all of the water nicely flys off the windshield at speeds above about 40 mph. In stop and go traffic when you may need to use the wipers, Rain-X may cause the wiper blades to grab and make noises on certain cars. Keeping the windows clean with an even coat of Rain-X and new wiper blades seem to minimize the problems, but not on all cars.