I cant say I know of a diff. between the K&n's.....besides waht is visually obvious. But im thinking that if you're wanting a cai you might wanna look into the volant, which i guess would be more a 'true' cai than the k&n as it utilizes the fender hole to draw in 'cooler' air whereas that one looks like its just chilling in the engine bay.
Im sure its probably a few more $, but to me the design makes more sense.