The former can actually work
Provided you can convince every single person to forsake their innate human qualities of greed and the desire to rise above others, then perhaps it can.
Communism relies on the elimination of "greed", whereas capitalism manages to make "greed" work for the better of all. You can't change the input, but you can certainly change the output. That's why most of the former communists have become "social democrats" - a way to get around saying one is socialist, because otherwise they'd be rejected immediately by the voting masses.
For the simple reason we all know that socialism, Marxism, etc., despite attempting to be secular religions, ultimately have the same result as spiritual religions when mixed with government: the blood, sweat, and tears of all the people it promised to help, as their freedoms are stripped from them and the old oligarchy is replaced with a new one.
...except if you happen to be one of the people who are naturally superior, by way of biology, and thus are meant to ascend to the upper echelons of society. The exploitation is merely the majority exploiting the minority rather than the "exploitation" commies see between the rich minority and the middle-class majority.
The point with communism is that everyone has what they need to survive, so there's no reason for them to want someone else's stuff.
No logical reason, perhaps. But since when have humans been logical? We are all dirty, greedy, selfish creatures deep down, and while communism and various religious creeds seek to change these raw qualities, capitalism exploits them for the betterment of all. In fact, that's the only thing capitalism exploits: human nature.
But capitalism systematically denies large parts of the population of these things, so there's every reason for them to want the rich's stuff.
Odd, considering Marxist theory requires going through capitalism first. I think it's pretty darned selfish to factor in the greatest evil in one's book into one's plans; if Communism was so perfect, it wouldn't require capitalism first. How can you hate those who will build your great society in the first place?
Funny, I always thought that government basically is "people enforcing the system". It always boggles my mind how all sorts of anarchists fail seeing this.
I was referring to the people at large, not their elected government or any small clique. There'd be no need for the government in either perfect capitalist or communist models, as the system would sustain itself and not require a force to maintain it.