One for people that won't wear helmets because they mess up their hair or make them look uncool, and that bike will have a rear-wheel-powering motor with enough torque to flip backwards at 1/8 throttle.
(mind you, there are some reasons I could accept for choosing not to wear a helmet, but those aren't them. 
)The other will have enough power to go from stop to lightspeed in a nanosecond, without leaving the rider behind. I might even put brakes on it.
