Solid rubber tires which don’t compress anywhere near as much as air are definitely more dangerous due to the fact that nearly all of the displacement from harsh riding surface irregularities or transitions have to be absorbed almost completely by the suspension. If you are not paying attention to your riding surface at all times, you are much more likely to lose your footing when riding a scooter with solid tires.
If you were/are a street skater, then you’re fine as reading the pavement at all times has become habitual for you. Anything that means big trouble for a street skater (manhole covers, road reflectors, drainage grates, brick roads, pot holes, etc) can also spell disaster for a solid wheel scooter rider at high speed.
All that being said, I love my modded (40 mph), solid wheeled Hero scooter.