I've had the Mopar splash guards and they rubbed so bad against the paint through the clear coat. I took them off and will never put them on again. Also for winter driving snow clung to them so bad that they were pulling off the body due to the cheap plastic rivets. The RPI's are cheap and many (not all) have reported that they break off very easily since it's painted plastic.
I would get the 3M coating over the front panels if I could do it over again. Right now I just apply Dr. Colorchip every year and it takes care of all my rock chips. Plus I think the Challenger looks much better without splash guards.