[Socialists/Ancaps] How can I be sure a socialist/ancap society will actually function better than a capitalist state?

I've thought about this. I don't have this issue with just socialism, I also have it with anarchism (capitalist anarchism). Why would I fight for a socialist takeover or an anarchist society when I don't know if it could work better than the capitalist state I am living in is currently working. I wouldn't be surprised if socialism or ancap can work as good, but how can we know if it will work better? How can I be sure? Convince me?