There was a significant difference, though:
Joseph, working for the Esterhazy Court, produced vast quantities of secular music in the form of symphonies, string quartets, sonatas (including over 200 for the Baryton – the Prince’s favourite instrument). He was less frequently called upon to write sacred music.
Michael, on the other hand, in the employ exclusively of Archbishops, wrote a substantial amount of church music. His output of secular music became more limited by the time he reached his mid-30s. In his day, there were those who rated his church music more highly than that of his now more illustrious brother.