I view the Stalin Model as something that was born out of necessity given the circumstances at the time rather than something that was intended to be the most optimal in the long run. The fascist invasion was telegraphed well in advance, and at the time there was no guarantee that the entire industrialized world wouldn’t gang up on the USSR to crush communism. The USSR under Stalin had no choice but to start building as much heavy machinery and weapons factories as they could ASAP, and the Stalin Model was optimized for that. Same goes for the purges, doing it wasn’t ideal but they had to root out turncoats before the Axis invasion began, Joseph Goebbels himself lamented that the USSR had done the purges in his dairy and believed it ruined their plans.

China under Deng by contrast had loads more breathing room. The US had just been defeated in Vietnam a few years prior reliving China of the possibility of US troops on it’s immediate border, and the West as a whole was still occupied with the USSR as it’s main enemy. When the US otherwise would of started messing with China under the George Bush Jr. administration the US’s attention got diverted again by the War on Terror, giving China even more time.