The private planning of corporations, whose budgets were sometimes bigger than those of governments, defined postwar American capitalism, not markets.
There may not be a practical difference between centrally planned economies by governments and by corporations, but there's definitely a moral one.
Governments can coerce their people into participating in their plans, but corporations cannot. They have to convince employees, customers, and other stakeholders that dealing with them is in their best interest.
The difference is analogous to seduction and rape. The end result may be the same, but there's a very clear moral difference between the two.
Governments have to convince employees, citizens, and other governments, agencies and organizations that doing the coercion is in their best interest.
Corporations can coerce people through unemployment, professional ruin (in the case of small professional networks), propaganda and other forms of information control...
Large, powerful organizations that dominate local economic and social landscapes are large, powerful organizations that dominate local economic and social landscapes; and it's not like people in one situation are somehow fundamentally different from people in the other.
If losing your job - or worse, keeping your job - restricts your choices as much as prison, does the moral difference matter? How close does the restriction of options due to un/employment have to get to prison for it to be a Problem?
Yes, there's a difference, and yes, there's a moral difference, and yes, governments have access to forms of coercion that corporations do not... but. Everything is still made of people, and if you can't leave - through actuality or perception - then it doesn't really matter.
Or, alternately, everyone gets a vote in the planned economy of the government. It is transparent, observable, and democratic. Only a tiny elite group of capitalists get to vote on the planned economy of corporations, which are as you say often bigger than governments.
Corporations need not convince people to participate; the impact of their plans and decisions have effects on the entire society, and they need not ask anyone their opinion first. The power structure in a corporation is a tyranny: disagree with the guy on top and you're forcibly removed. Toe the line, suck up, and maybe you'll move higher in the pyramid.
I don't need to make an analogy: there's two distinct methods for decision making here; tyranny and democracy, and I know which one I'd choose. There's a very clear moral difference between the two.
Voting makes people feel powerful in the same way that playing the lotto makes them feel rich.
The issue with voting, or any exercise of voice, is that it is a positional good; i.e. "winner-take-all" [1]. Even if everyone has one and only one vote, power will tend to accumulate in the hands of a few "influencers". It is easy for influencers and rulers to serve each others interests, directly or indirectly, while by-passing the rest of the population.
If we are doing an apples-to-apples comparison - government centrally planned economies vs. corporate centrally planned economies - then yes, the ability to exercise voice is a point in favor for economies that are planned by governments. However, I find it to be a rather weak point. That corporations are limited in what they can do to individuals (they can't imprison, kill, rob, etc.) and that they are subject to tort and criminal law, is much more essential to liberty, justice, and self-governance for the general population.
The idea that the American economy was centrally planned in 1967 or any time after that, is laughable. The government has made policies and enforced them, but no one is telling IBM how much R&D to allocate to chip research, except IBM's stake holders. And the reference that US corporations sometimes have budgets larger than country budgets is unimportant in the context of the overall US GDP. Apple's economy is dwarfed by the US's, and their ascendance to massive wealth proves the point that the US economy is built on the disruption of established markets.
I can think of no actual centrally planned economies that pay more than lip service to democracy, nor any that have compared favorably with free-er market economies in improving the lives of the average person. Humans tend towards corruption, and free markets are the best tool we have for managing that. Want to see brutal, selfish, horrifying corruption, just look at your local centrally planned economy where the greed represented by a McDonalds happy meal campaign is instead implemented by the local police force.
Governments have employees. They also have customers in the form of the populace and stakeholders in the form of voters and lobbyists. I'm not sure I see the difference.
There may not be a practical difference between centrally planned economies by governments and by corporations, but there's definitely a moral one.
Governments can coerce their people into participating in their plans, but corporations cannot. They have to convince employees, customers, and other stakeholders that dealing with them is in their best interest.
The difference is analogous to seduction and rape. The end result may be the same, but there's a very clear moral difference between the two.