Okay, I'll bite and am intrigued. If PPP is more realistic and better reflects military output, shouldn't the USSR be significantly larger? It was turning out way more weapons than the Germans in WW2, after all.
That depends on how much of the GDP was used for military production of course.
Now to elaborate on my PPP is a better representation reasoning: PPP represent the industrial output as a function of the domnestic value assigned to the products. As both countries were striving to be as autarkic as possible, the domnestic value (thus PPP representation) of products was what played
the major role in determining the output of the military industry.
But GDP (nominal or PPP) is an indicator of the intrinsic capability of the economy to sustain a certain level of military production, not the actual output. But you know that too.
It was just that Nazi Germany was criminally inefficient regarding its application of military production.
For example, during 1941-43, Nazi occupied territories produced way more steel than the USSR, but the Soviets still built more tanks...
Or to turn your argument around, with a nominal represtenation of the GDP, the difference between Germany and the USSR would only increase more in the German favour, giving an even more skewed comparison when we take into account the actual military production.