What are the differences between the Chinese tree peonies and the Japanese tree peonies?

The Chinese peony has more varieties in color, flower shapes, flowers sizes and in fragrance. There are more cultivars which grow in a wide range of temperature zones in China. The Japanese tree peony originally came from China. They have been developed and cultivated according the Japanese taste and preference, for instance, there seem to be more single-petaled varieties where as the Chinese prefer the double-petaled tree peonies.