What is equality?

I recently had a conversation with a friend in which he criticized capitalism because it was unequal. I responded with Jesus parable of the laborers in the vinyard in which people were hired at various times in the day to harvest grapes and then they were all paid the same at the end of the day. Were they treated equally? Yes and no. They had equality of outcome, but they were certainly not treated equally for labor performed, either by the hour or the quantity of crop harvested.
Political or economic equality can be equality of outcome, opportunity, laws, lack of legal barriers etc. The notion of equality does not tell us on what basis the equality is to be drawn. What basis we decide to administer equality can often have great impacts on other factors. Socialism, for example, tends to make everyone equally poor, except for the oligarchy that administers the socialistic system. Capitalism treats everyone equally in the sense of equal before the law, but it results in great inequality of wealth. Which is best? The notion of equality itself does not tell us.