China's population can be misleading. China has over 1.4 billion in population but due to its huge area, it only has 390 population per square miles. Meanwhile, India has 1,130 population per square mile which is nearly three times as many compared to China.
Huge or low population density has its cons and pros. Lower population density countries are less likely to fast-track their resources but unemployment might not be a concern. Whereas huge population density countries if utilized well can quickly exploit resources and drive their economy bigger. Failure to do so can lead to unemployment, very cheap labor, and other issues that reflect a lower GDP per capita.
China vs India is not exactly an apple to apple comparison. Most of India's land is suitable for agriculture, but in China that is not the case. More than half of the surface area is in the provinces of Xinjiang and Xizang, where the conditions are very arid and not suitable for agriculture. Provinces such as Qinghai, Inner Mongolia and Gansu also have similar climatic conditions. On the other hand, only around 10% of India is arid.