What is the advantage of using human development index in making comparison between countries?

One point would be that HDI incorporates policies such as health and eduction. This means that it can better represent the impact of governments as it demonstrates the impact of the supply-side policies they can utilise. Furthermore, due to the fact HDI comprises of expected years in education and life expectancy at birth, HDI serves to illustrate the potential development of a country's living standards as it might take time for an increase in expected years of education to affect GDP and living standards.