The electric scooter is Substantially much easier to manage on account of the steering deal with and physical brakes. Riders can adjust their foot placement with no difficulty or danger.
That said, the electric skateboard is A lot a lot more thrilling to ride (in my opinion). Steering is handled by balance exclusively and with nothing at all to hang on to, you have got to anticipate inertial forces ahead of they hit you (lean forward ahead of you apply power, lean backward just before you apply braking). Also, rearranging your feet while riding is far more complicated as shifts in weight have an effect on your steering.
As someone who has logged numerous hundreds of miles on each kinds of rides, this is a strong informed opinion.
That said, that is largely a matter of preference. Both may be ridden successfully and safely in just about any context with cautious consideration and safety gear (put on a helmet at the least).
Skateboarders slow down by slowing their bodies. The board is trapped under their feet so it stops also below the rider’s control. An electric skateboard (or scooter) with brakes, slows down by applying friction towards the ground by means of the wheels. The rider must cease their body’s forward momentum through their make contact with with all the board. Scooters possess the pole and handle bar to this effect, whereas skateboards have nothing but grip tape so I'd say scooters are much less unsafe.
So there is not specifically conclusion which one is much more harmful. All we are able to do is usually to wear all essential gear and ride them properly.