By the metric of rate of crime, rate of poverty, rate of illness. Things like that. Communism done right far exceed the performance in those areas than capitalism does. Capitalism encourages individuals and crime is all about individualism. Communism encourages communal thinking, making it more difficult to commit individualistic crimes and giving less incentive to commit crimes.
For example, if all your money is regulated by government, then if you try to steal money from someone else, you wont be able to use the money because you got it from unknown origins and communism done right does not accept money from unknown origins. Thus stealings maain motivation sis eliminated