There is also the issue of incentives. In a pure capitalist system it's sink or swim so everyone has a strong incentive to bust their ass. In a pure communist system, there's very little incentive to work since effort and pay are completely separated.
A more esoteric issue is emergence. The tendency of complex systems to self organize naturally in ways that are often superior to what we can achieve through a careful top down approach. What Adam Smith called the Invisible Hand.
“As every individual, therefore, endeavors as much as he can both to employ his capital in the support of domestic industry, and so to the direct that industry that its produce may be of the greatest value; every individual necessarily labours to render the annual revenue of the society as great as he can. He generally, indeed, neither intends to promote the public interest, nor knows how much he is promoting it. By preferring the support of domestic to that of foreign industry, he intends only his own security; and by directing that industry in such a manner as its produce may be of the greatest value, he intends only his own gain, and he in this, as in many other cases, led by an invisible hand to promote an end which was no part of his intention. Nor is it always the worse for the society that it was no part of it. By pursuing his own interest he frequently promotes that of the society more effectually than when he really intends to promote it (Wealth of Nations. VI, ii. P.456).
Neither global capitalism nor the economic system of the US (although the 2 are probably interchangeable) follow the model of economic nationalism that Smith is describing in this quote (note the clear references to domestic industry and the preference of it towards investment in foreign industry).
Furthermore note the usage of the word frequently - which does not mean the same as always.
Smith was clearly far more in favour of regulated markets than his more staunch supporters ever care to admit