The first trip we made in our new coach in 2006 peppered the toad's front end pretty badly. I put a Roadmaster Guardian on and sure wish I'd done it before that first trip. It's easy to assemble and take apart, and stores on the back of the coach with the optional Stowaway while parked in campsites. I've considered the Roadmaster Tow Defender as extra insurance, but the Guardian alone seems adequate.
The Karguard appears to be less expensive, but not so much that I wouldn't buy a Guardian again because I'm simply a fan of Roadmaster's engineers. Regardless, I'm sure the Blue Ox one would stop just as many rocks.
I'd not give 2 cents for a "bra" type hood cover, because they trap dusty grit underneath that scratches paint and does more harm than good.
Joel
