"Under capitalism, man exploits man. Under communism, it's just the opposite." which seems to be attributed (without any sources) to John Kenneth Galbraith:
I've also seen it as "Under capitalism, man exploits man - under communism it's the other way around." I always assumed it was a translated Russian proverb, along the lines of: "No truth in the news and no news in the truth" (Major Soviet papers were "Pravda" (the truth) and "Izvestia" (the news).