I think a motorcycle is much, much safer. With the motor you have the option of staying with or ahead of traffic. You don't have to ride to the extreme right of the lane as cars squeeze by. On the pedals you're at the complete and total mercy of every car that overtakes you, zipping by inches away with enough speed differential energy to knock you out of this life with the merest inattention/indifference of the driver.

Even so I enjoy riding the pedal bike so much more than a motorcycle.