In my old age, I find myself in the odd position of arguing the left side to the right and the right side to the left. Lately, it's been the patent absurdity of hearing the moderate liberal Barack Obama called a "socialist" as if that were true and, if true, would be bad.
Neither socialism nor capitalism exists in the real world, although both have heaved and tugged mightily to attain purity.
The Democratic People's Republic of Korea, I hasten to add, may have achieved pure socialism, but I submit that none of us is sufficiently informed to know for sure.
I cannot imagine how anything close to pure socialism could be achieved outside of a police state, because black markets are always the beginning of the end and therefore must be suppressed without mercy. You can easily start a quibble about "ownership of the means of production" and we get off into "of what size?" and the bottom line is in any moderately complex society there is collective ownership by the political form (socialism) or by the corporate form (capitalism) and the differences play out such that each can only "succeed" to the extent it takes on the best features of the other. While the faithful on each side insist there are no "best features" in the other.
And therefore a quick scan of every economy in the world where any sane H. sap would want to reside renders the the argument a silly waste of time and energy. The only issues seriously on the table are what is the proper mix and how does it inform the immediate choices?
Beyond that, the argument about capitalism and socialism is better pursued in churches or the functional equivalent.