As a purely "style" question.
Which style of jumping in are we doing?
Style A- the vehicle becomes an extension of the riggers body, extra limbs and organs so to speak, through which he/she can feel and act instinctively. Special effects wise, this puts the rigger leaning with the motorcycle, sitting with hands of the wheel of the car, what have you.
Style B- The vehicle replaces the riggers body, so that he/she no longer has arms, legs etc, only wheels, rotors, whatnot. Special effects wise, this leaves the rigger comatose and flailing about inside a car, or seat belted to a motorcycle to keep from falling off.
personally, i lean toward A, but it's your call, dude.