It's the learning curve that makes 3 wheelers dangerous. If you are used to a bicycle or motorcycle you'll most likely
lean "the wrong way" in a turn, put your leg out for balance and run over your leg. There is also a problem
of too much speed in a turn with resultant rollover. Here in California OHV parks banned them for that reason.
Once you get passed the learning curve, 3 wheels are fine and can be a bargain.