What was the significance of the Sino-Japanese War for China? For Japan? Why? Was its imact of lesser or greater importance than the later Russo-Japanese War?
One led to the other. It was Japan's victory in the Sino-Japanese War that caused Russia to take a more active role in China, including sending troops to quell the Boxer Rebellion. This policy culminated with attempts to cultivate Russia influence in Korea, as well as in Manchuria, which ultimately led to the war with Russia. So basically, the Sino-Japanese war established the conditions that led to the Russo-Japanese War.
Japan often seems to have felt threatened because it is a small, water-locked country and does not have any opportunities to grow. Yet the fates of China and Japan will always be somewhat interconnected, so there are many long-standing effects from that war too.
I'd say the Russo-Japanese War was more important for Japan psychologically and in geopolitical terms. Defeating China was one thing, but defeating a European power really put Japan "on the map." It also gained some measure of revenge for the Triple Intervention that robbed Japan of some of what it gained in the Sino-Japanese War.