You're both conflating economic systems and political systems. Marxist communism is not authoritarian — it is anti-authoritarian (withering away of the state and all that). The only kind of communism that you are familiar with is authoritarian communism (Stalinist USSR, Democratic People's Republic of Korea, etc.). Marxist communism, like Christianity, has not so much failed as it has never been seriously tried. It is simply not feasible for a large, manufacturing-based nation-state; at best it can only be sustained in a small agrarian commune or kibbutz. The People's Republic of China was able to keep (economic) communism alive as long as the economy was primarily agrarian. With the rapid expansion of the manufacturing sector of the economy, the PRC has had to move toward market capitalism as an economic system (at least in the manufacturing sector; they also had to move from a dictatorial political system to a merely authoritarian one).

But the reason that the USSR and Nazi Germany and the Bush administration all look similar in not because of their economic systems, which are all different, but because they are all authoritarian regimes. The economic systems merely determine who owns what and who works for whom, but the political system determines who gets a say in who does what to whom. It doesn't matter what the economic system is, from the outside authoritarian regimes will all look the same.

[Insert favorite Lord Acton quotation here.]

USA Ranking on Economic Competitiveness: #6
(#1 Switzerland and #2 Finland)- World Economic Forum Report (2006-2007)
http://www.weforum.org/en/initiatives/gcp/Global%20Competitiveness%20Report/index.htm

USA Ranking on Mothers' Index: #26
(#1 Sweden and #2 Iceland/Norway)- Save the Children Report 2007
http://www.savethechildren.org/newsroom/2007/best-worst-countries-2ba-mother.html

USA Ranking of Student Reading Ability: #12
(#1 Finland and #2 South Korea)- OECD PISA 2003

USA Ranking of Student Problem Solving Ability: #26
(#1 South Korea and #2 Finland)- OECD PISA 2003

USA Ranking on Student Mathematics Ability: #24
(#1 Hong Kong and #2 Finland)- OECD PISA 2003

USA Ranking of Student Science Ability: #19
(#1 Finland and #2 Japan)- OECD PISA 2003

USA Ranking on Women's Rights Scale: #17
(#1 Sweden and #2 Norway)- World Economic Forum Report

USA Position on Timeline of Gay Rights Progress: #6 (1997)
(#1 Sweden 1987 and #2 Norway 1993)- Vexen

USA Ranking on Journalistic Press Freedom Index: #53
(#1 Finland, Iceland, Ireland and the Netherlands tied)- Reporters Without Borders 2006

USA Ranking on Political Corruption Index: #20
(#1 Finland, Denmark and New Zealand tied)- Transparency International 2007
http://www.transparency.org/policy_research/surveys_indices/cpi/2007

USA Ranking on Environmental Sustainability Index: #45
(#1 Finland and #2 Norway)- Yale University ESI 2005

USA Ranking on Climate Change Performance: #53
(#1 Sweden and #2 UK)- Climate Action Network 2007

USA Ranking on Infant Mortality Rate: #32
(#1 Sweden and #2 Finland)- Save the Children Report 2006

USA Ranking on well-being of children: #20
(#1 Netherlands and #2 Sweden)- UNICEF Report Card 7 2007

USA Ranking on Human Development Index (GDP, education, etc.): #10
(#1 Norway and #2 Iceland)- UN Human Development Report 2005

But the three regimes do not look the same from the outside despite authoritarian elements in each. Authoritarianism manifests in ways heavily determined by the economic system and cultural characteristics. In the US, about half the population willingly participates in empowering the regime, falsely believing it to be in their best interests. In the USSR, very few had any choice about anything. In Nazi Germany, an unstable situation quickly evolved into a dictatorship with support of the industrialists.
— Mike Sulzer

But you're still conflating economic systems with political systems and you're still looking at internal differences in pointing out the variations in the systems. It doesn't matter what economic system the authoritarian state uses to direct the means of production to the advantage of the state.

It doesn't matter if the means of production are (nominally) held in common by the people or the means of production are owned by corporations controlled by the government or by corporations that control the government. The result is the same: production is directed toward the policies of the state. All you see from the outside is intense militarism.

It doesn't matter if the information provided to the populace is determined by a Ministry of Information and Propaganda or by an official state news agency or by a corporate-controlled mass media masquerading as a "free press". The result is the same: information available available to the population is strictly controlled and news blackouts are common. All you see from the outside is a highly nationalistic state that constantly justifies its militarism.

It doesn't matter whether enemies of the state or society are kept in Konzentrationlager, in a Gulag Archipelago, or in federal and state prisons or at "undisclosed locations". The result is the same: a significant portion of the population is incarcerated for more or less arbitrary reasons that involve skin color, ethnic group, or political or religious beliefs rather than any criminality. From the outside you usually don't see anything at all because the state-controlled media doesn't mention it.

One could continue the list, but there is a 1000 word limit. The point is that when you look at an authoritarian state from the outside, it doesn't matter what its internal economic system is or even how it got to be the way it is. All you see is a militaristic and nationalistic state where the means of production are firmly wedded to the government.

L.W.M.: Nazi Germany, Czarist and Stalinist Russia, and Maoist China were all privately owned states, and not even nominally.

In Marxist communism all property is held in common by the people. Didn't you ever wonder where the word communism came from? Maoist China was called the People's Republic of China. Nominally, (yes, nominally only) the state belongs to the people. Snap out of it.