My observation is that a free-competitive market is more efficient than government ownership, but government ownership is more efficient than government-regulated monopolies. That is true for electric utilities:
EIA data examined by the American Public Power Association showed public utility rates are on average about 13% lower than those of investor-owned utilities.
Publicly owned utilities ‘not a panacea’ but can produce customer benefits | Energy News Network
With electric utilities, the product is well-defined, and components like generators and transformers are available from a competitive market. The differences between state-owned enterprise and regulated monopoly are not that large. For the military, most of the weapons and major components are custom-made, so the possibilities for corruption and inefficiencies are far greater.
In contrast to the American defense industry that is dominated by a hand-full of privately owned contractors, the Russian defense industry is predominately government-owned. The exception would be for components with a large civilian usage with a competitive market.
In the Russian system, the military has direct control over weapons’ production and has incentives to maximize bang for the buck / firepower per ruble. In the US system, contractors have incentives for producing small quantities of super-complex weaponry while gaming and corrupting the oversight system to maximize their profits.
If you doubt that consider the $1.5 trillion spent on the F-35 fighter. The US has spent more on this one weapon than Russia has spent for its entire military for decades, but Pentagon simulations show that Russia could easily defeat the F-35 in a serious war:
“In every case I know of,” said Robert Work, a former deputy secretary of defense with decades of wargaming experience, “the F-35 rules the sky when it’s in the sky, but it gets killed on the ground in large numbers.”
US 'Gets Its Ass Handed To It' In Wargames: Here's A $24 Billion Fix - Breaking Defense
From what I see, the Russian model for military procurement works far better than the American model, but there are huge vested interests in keeping what we have in the US.