Nittaku J top is literally the best investment I ever made when needing balls. I typically used them in training before I had any comp that used nittaku premium. These balls were vastly different to the rest of the balls, at the time.
Nittaku J top as a 1 start ball, was still so similar to its counterpart 3 star ball, Nittaku Premium. Whereas, a dhs 1 star vs 3 star is a huge difference. Hope this helps