Well Dark Object Subtraction is a very basic method, and not very accurate, as it does not account for the atmospheric transmission, which is reduced in presence of aerosols. Sen2cor should perform better, especially if your image is a green one.
But I can’t tell you more, I am not an expert of both softwares, I have my own one : http://www.cesbio.ups-tlse.fr/multitemp/?p=6203