When it comes to military strategy, the Romans have a clear cut methods that are well documented. Everything was well organized. They have well trainded army, good standardized equipment, organized formations and hierarchy. Personally, I think the Roman military somewhat revolutionized the military system.The site,
Roman Legion gives nice details about the military formation, march position, skirmishers, military camps, military equipment and enemies of Rome.
On the Chinese side, there seems to be no coherent military records in Ancient China because the military organization technically depends on which dynasty and who are the rulers. There are times when they had good cavalry forces from the northern portion of China, but the Chinese territories was not quite stable in some dynasties. Despite this, the Chinese have developed a unique arsenal of weapons such as crossbows with quick ammunition and some fire other weapons using gunfire. In the site,
Chinese Siege Warfare, you can see a wide range of siege weapons. Another interesting fact about the Chinsese is that they use other methods to appease their potential enemy. They tried to have good relations with neighbor enemies by offering (silk) trade and political marriages. Sometimes, they can go to extreme measures to win a battle. When a certain Chinese general was on the losing side, he ordered the condemned criminals to go into the front lines and commit suicide. It basically scared the hell out of the opposing army, which simply run away. Despite all of these, the Chinese never really had a good centralized army organization because it changes depending on the ruler at that time.
In terms of all out war, the Chinese has some disadvantage with its unstable leadership and military organization. Ancient China do not always have a reliable army because it changes with the ruler and political situation at that time. In this case, it is more safe to bet on the Roman legion.