"High-altitude winds between 1,640 and 3,281 feet (500 and 10,000 meters) above the ground are stronger and steadier than surface winds. These winds are abundant, widely available, and carbon-free.
"The physics of wind power makes this resource extremely valuable. “When wind speed doubles, the energy it carries increases eightfold, triple the speed, and you have 27 times the energy,” explained Gong Zeqi "
What matters is scalability and how much material and cost you need to produce per energy unit. Kites (either parasails or fixed wing) are much simpler, can be scaled up too, and you only need a simple cable that pulls the generator’s winch. Overall kites seem much more efficient to scale up.