Is GDP per capita or per capita PPP more accurate when it comes to measuring one country's quality of life?

Per capita GDP does not tell you about drinking water or child abuse for crime rate,suicide rate etc. Among countries,they don't have enough data to make it comparable. It is only for ranking gesture.

PPP is just the purchasing power of the equivalent local currency. So it is best to compare per capita GNI (Gross national Income) not GDP after it has been corrected based on PPP of the local currency. The World Bank does a good job of making this comparison. The info is on Wikipedia.

The only problem with this is it does not take into account the way the income is distributed. The rich may be really rich, but the poor may be really poor. So a plot of income distribution in the population should help determine the quality of life. BTW a flat distribution where everyone makes the same amount would not be an indication of freedom. A smooth bell curve would be the most likely indicator of a free country.