Are we talking about a revolution or a government, here? If you believe the revolution is ever-ongoing, fine, substitute your own words for the taking-power part and the governing part. If the taking-power part, I’m not sure we can know. Look at the Iranian Revolution. There were leftists involved with the taking-power part, but not so much with the governing part. As far as a government for the people, there are probably many different ways it can turn out, but the essence is fulfilling people’s basic needs while also respecting their human rights. No one’s gotten it right yet, but that doesn’t mean we can’t.
No, I don’t think it’s arrogance. I’m not saying we have the answers, I’m saying we need to keep trying, because our past attempts were insufficient. It’s not arrogant to try to learn from one’s mistakes. And it’s not arrogant to assume that a movement’s chances of success can be altered by changing material conditions.
I’m well aware that in many cases, authoritarian socialism/communism has improved material conditions for many people. But I also notice that not a lot of Westerners defending these governments attempt to move there. All our current systems are fucked, and acknowledging that is awareness, not hubris.
In answer to your question of “which is better,” it probably depends heavily on the preexisting local circumstances. But I’m from the US, so I’m sick of being forced to choose between two shitty options in a false dichotomy. Neither. Neither is better, and we need to stop pretending what exists now is the end of political and economic philosophy. It’s not. We need to do better.