I have driven hundreds of miles with both kinds. I consider the brush to be junk not worthy of having on the vehicle. I installed a clear across the back solid flap with 4 inches of ground clearance. It works just great, except when backing in to parking places. Mine was hung on a jointed hanger so it was not too bad even on that. One draw back was: if I ran over a rubber alligator (you are not going to miss all of them). Some will get up under the solid flap and really raise cane before it exits. Never had a serious situation from that however.