Vadim, you are hereby sentenced to death by guillotine for your foolish blasphemy.
Judas Priest, easily. Not only are they far more consistently good than Maiden, as Iridium said, Maiden's entire career was based on the ideas perfected in Stained Class. The song structures, lead guitar melodies, galloping riffs, emphasis on choral melodies, and triumphant mood are all to be found on that complete work of genius.
That isn't to say Maiden isn't a great fucking band, because they are. Priest was just a great fucking band before them.