Resumen: This paper seeks to compare income distributions from the opportunity advantage viewpoint. That is a measure of how likely it is for a representative individual of one society to receive a higher income than a representative individual of another. Opportunity advantage tries to measure the income opportunities a society offers to an individual, relative to other societies, evaluated from the «veil of ignorance» viewpoint. We show that this notion can be precisely formalised and results in a complete and cardinal income distribution evaluation. We also present an empirical illustration of the gender differences in wage distributions in Spain after the financial crisis. The results show that this criterion offers new insights into the evaluation of differences in opportunity.