The main difference is that RallyArmor flaps are floppy, and more of a "rally style" flap. Rokblokz (or the ones I have, which are GORILLA brand) are stiff plastic that doesn't flap around. The larger RallyArmor flaps make sense for an off-road vehicle, but I think they look silly on our cars. Also, the RallyArmor flaps mount using an additional bracket, and I don't like that mounting method. The GORILLA rock guards bolt right into the fender well (into existing holes) and it's a cleaner, simpler, sturdier install, IMHO.
A lot of people think they're just a style thing. I did NOT install them for style reasons. I installed them because I wanted to protect the paint on the side of the car from rocks. When you upgrade to a 9" wheel, lower the car slightly, and put a few degrees of camber on it, the bottom of the wheel is much further out. Then put sticky Michelin Pilot Super Sports on the car, and rocks start to be flung into the body work. I also autocross the car with RE71Rs, and those basically sandblast the car.
These are
the ones I purchased. I wound up trimming about 3/4" off the bottom of them because I was barely scraping them on the ground during the more violent transitions in autocross. Rokblokz sells a "shortie" version but they are TOO short for my tastes and looked weird since they didn't even clear the bottom of the rocker panel.
