A very valid question indeed. 3-wheelers are known for their highly impressive turning radiuses, but when it comes to stability, nothing trumps a 4-wheeled All Terrain Mobility Scooter.
On the other hand, if you’re a tall individual then you might might prefer 3 wheels as it will allow you to comfortably rest your legs on either side of the tiller. Furthermore, 3-wheelers also have a lighter “heaviest part”, which may make it easier to carry them around while you’re traveling.
Weigh in your circumstances, and then decide which wheel configuration is best for you. With that said, the stability and sturdiness required on off-road surfaces while traveling at high speeds is best served by 4-wheels.