This is a fantastic question.
Let me made a general statement first about culture and technology. When there is culture in the ancient world, technology follows. This is the case with both the great civilizations of China and Mesopotamia.
Now as for geography.
Both civilizations were able to flourish, because they were great river societies. For example, in Mesopotamia the land is between the Euphrates and Tigris rivers. Also both rivers are fed by numerous tributaries, which is important for agriculture. Without these rivers, no great civilization would have been possible.
As for China, the same is also true. The cradle of Chinese civilization can be found along the Yellow River. For the Chinese, this river is called mother river. This is why the Chinese see themselves as the children of the Yellow River. This is not an overstatement, as from the Xia (21st-16th century BC) and Shang (16th-11th century BC) Dynasties to the Tang Dynasty (618-907), the Yellow River area was always the epicenter of culture, power, and development.
For a comparison, all you need to think about is the Nile. Egypt was able to form a great civilization as well, because of their river system. In this, sense, rivers (that is geography) make all the difference.