The thickness of Pu can be seen first. The thicker Pu is, the thicker PU coating is required so the stronger Pu will be, and the better the quality the PU is.
It can also be observed that the thinner the bottom of the PU is, the worse the quality is, because the stress of Pu is mainly on the cloth bottom, and the PU coating is completely free of force.
In addition, you can believe the touch of Pu, with good quality feels thick when touched. And you can torn the PU properly, for those that are not easy to deform will be better.