the rtr will have less bling and hopups. I am not sure on specifics wiht the 8, but usually the kit is more of a pro version. Beefier shock towers, aluminum center braces etc. The extra hop ups etc is there in exchange for an engine and crappy radio system.

Get the kit, learn the vehicle by building it, and then you can put in your own elctronics and engine... Best way to do it IMHO