There are pros and cons to both estimates.
One problem with PPP, is that its reliant on a very low frequency survey (once every 5 years, once every 10 years on some stuff too) for the prices of consumption goods....
That’s one problem with PPP. The other problem is that when you build foreign reserves, pay down your debt, or when you conduct trade with other countries, you don’t do it in PPP dollars. You do it in nominal dollars.
If a country wants to import oil, copper, fighter jets, ammunition, etc., it pays the same price regardless of its PPP indicator. The US pays the same as Bangladesh or China when importing oil or copper.
When someone says China has a bigger economy than the US, because of the PPP adjustments, it is misleading, because the PPP adjustments doesn’t translate into purchasing power on international markets.
If you have two countries with equal GDP in PPP terms, but one has double GDP in nominal terms because local prices are twice as high, their economies are not equal. The country with higher nominal GDP has much more purchasing power for imports of raw materials, technology, weapons, etc., or to make investments.