It's an incomparable experience.
Security is really the same as any bike, though it's much harder to steal the wheels!
On acceleration & max speed, obviously it depends on the particular scoot, but mine is much better than a typical human on a bike. That's a Ninebot Max, costing about £600 ish
Yes. It takes a few hours to learn to ride an EUC. But I'd wager that EUCs are safer because of that. Most accidents on rental scooters happen to first-time/occasional users. The fact that you need to learn how to ride an EUC gives you an appreciation of how bad things can go if you push farther than your skill allows.
In the end, EUCs are safer (larger wheel doesn't get locked in small potholes), more comfortable even without suspension, break faster due to more powerful motor, and are more compact.