The purple controller is more pleasant to use than the turquoise one. The same applies to the regular set, of which the blue one is more comfortable than the red. This is primarily because the joystick on the purple one is positioned further to the left, making it easier to reach. For children, that makes the difference between being able to operate the controller or not; for older people, it makes the difference between getting cramps or not. Secondly, those controllers do not have a home button right under your left thumb, which you could accidentally press, suddenly throwing yourself and others out of the race...
Incidentally, the controllers for the Switch 1 also had this problem. It is because the controllers can also be used together as a single set. People who use them in that way, or play with fewer players at the same time, will be less bothered by this.
Furthermore, as far as I know, there are no better alternatives. So, the 'fight' over the purple and the blue remains for a little while longer...