The Knife is considered to be a more user friendly car. You do not have to tape the batteries to the chassis, there is no t-bar to tweak or break, and the Knife seems to hold a tweak setting longer than a car with a fiberglass t-bar.
The red Knife also comes with the tires fit for racing, (purples, and greys) and lowered rear pod plates so you get more use out of the rear tires.