Prices in a capitalist system are information signals that inform the system how to allocate resources. If you do away with the pricing information (by setting mandatory prices, for example), you break this and usually end up with large surpluses or shortages. Getting other people to inspect the system for inefficiency and remove it is less efficient than using prices for the same purpose.
If a command economy were capable of producing on the same level of efficiency as a private one, then Stalin's various five year plans would not have starved millions and the collective farms might have actually worked. As it is, they didn't and Soviet Communism just wasn't very efficient.
There was also the fear and terror the country was ruled by, resulting in a state of constant paranoia among the citizenry. Not to mention the cronyism inherent in that system, by which only the most "loyal" (not to the state, but to their bosses) had any kind of future. And then there was the massive and vicious oppression and persecution of various minorities across the nation, and of the nationals of the various countries which the Soviet Union invaded and absorbed.
And even at the start of the Soviet Union, there were the millions who were killed during the Russian revolutions, which radically restructured the societies which made up the Soviet Union.
All these factors and many more contributed to the downfall of the Soviet Union. It's just not nearly as simple as saying that "capitalism is more efficient than communism".
Um.. No. I explained some of the reasons why the Soviet Union collapsed. No other "centralized system" had the particular history that the Soviet Union had. It was absolutely unique. And I can see no reason why any other "centralized system" must have all, or even any, of those negative factors which caused the Soviet Union to collapse.
"even if you remove all those problems a centralized system still can not beat a capitalistic system with its superior capital allocation via pricing mechanisms"
This statement of yours sounds like an avowal of ideology (an ideology that's sadly all too prevalent on HN), rather than any sort of argument in favor of capitalism or against communism.
"Somebody not in the favored central government is going to want to be in the favored central government clique, and in the absence of other mechanisms to keep them in check (like letting the market decide who wins or even having both win), it's going to turn to violence."
Are you saying that "favored central government cliques" and violence aren't possible in capitalist systems? Even a superficial look at a model capitalist country like the US will reveal their presence.
No, it's a reflection of Economics 101, really. You simply can not replicate the amount of information in a price in a centralized system, it's actually impossible.
Walk through the first few chapters of http://www.daviddfriedman.com/Academic/Price_Theory/PThy_ToC... . No, seriously, do it. The first few chapters are very basic and if you can just wave them away as "ideological" then we're done here anyhow. Prices contain a lot of information and no central authority can match it. They especially can't match it if they believe prices are a moral issue and they ignore the basis of them in the first place.
"Are you saying that "favored central government cliques" and violence aren't possible in capitalist systems? Even a superficial look at a model capitalist country like the US will reveal their presence."
First, the US is not a model capitalist country and has not been in a long time. The idea that the US is some sort of unrestricted capitalist paradise is propaganda, not fact. Second, your logic here is terrible. When I say that the only outlet for advancement is one or another form of violence in a centralized system, therefore I am claiming that in a capitalistic system it is never a form of advancement? If you're not even reading my actual points and you're willing to bend what I'm saying that hard, or you can't even see the grievous crime against logic you just committed, that's not even worth replying to.
It's not like the USSR was unique historically. China, Vietnam, and North Korea also attempted similar systems. Of the three, two have effectively admitted defeat and are now pursuing progressively free-market systems while the third hasn't, and is a Hell-hole as a result.