The core processing contrast is simple. Japan generally halts oxidation with steam soon after harvest. China more often uses dry heat, especially pan-firing, to do the same job for green tea. That is why Japanese green tea usually keeps a brighter green color and a more vivid vegetal profile.
In flavor terms, Japanese tea often lands in the world of cut grass, sweet greens, seaweed, spinach, and broth-like umami. Chinese teas, depending on category, can move toward roasted nuts, orchids, honey, dried fruit, wood, minerals, or earth. So when someone asks about matcha vs Chinese green tea, the answer is not only powder versus leaf. It is also steamed shaded intensity versus a looser family of dry-heat, leaf-infused styles.
Oxidation widens the gap even further. Japan is strongly centered on green tea, including gyokuro and roasted green tea like hojicha. China, by contrast, includes a complete spectrum of oxidation and fermentation styles, which is why it can offer delicate white tea, floral oolong, rich black tea, and aged pu-erh alongside green tea.