This morning on my way to work the driver of the bus I was in stopped at traffic lights (that were green) to help a person with an electric wheelchair across the road. The reason he needed help was because he was stuck in a bank of snow that a snow plow had pushed at the side of the road.
You can get a joystick controlled chair that can go off road, and put knobby tires on most chairs. It's a matter of money and mess for those who are in chairs.
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In this case it has to do with the design of the chair.
It's a pretty big leap to assume this design an improvement in how a chair is controlled, especially by a quadriplegic.
It would be a matter of preference for most paraplegics, but that's generally a matter of convenience. From that point of view I don't think this is an improvement at all over a joystick.
Joysticks are very intuitive and require almost no effort. Leaning back and forth and side to side is not so intuitive and requires a lot more effort.
One thing this chair does offer is "fun". I think it's cool as can be and I'd love to take it for a spin.