Which are better, single-wheeled heelys or double-wheeled heelys?

I learned how to use two wheels first.

Now I use one wheel. Heelys, also known as Heelys, originated in the United States. With its tangible design, safety, and novel concept that allows people to perform roller sports anytime and anywhere, it has instantly become a new generation of leisure sports for teenagers after scooters. The appearance of Heelys shoes is no different from ordinary sports shoes, except that the heel of the sole has a small detachable wheel than ordinary shoes. The heel is 3 to 4 centimeters higher than ordinary sports shoes, and the weight of the entire shoe is about twice that of ordinary sports shoes of the same size. After putting it on, you can choose to slide or walk at will. The gameplay of Heelys Shoes is rich and colorful, including sliding and various fancy gameplays. You can also create new gameplay by yourself. Sliding in Heelys shoes has certain risks. Wear protective equipment when gliding, and pay attention to the occasion and venue. Do not choose to skate on busy streets or public roads, and do not force skate on uneven or slippery roads. Once the child falls, the momentum is relatively high and it is easy to cause injury to the child.