But you can easily compare two genres... and it also works when two bands are the same genre, because no music is perfectly defined by a genre. In the end you could compare anything in some way. And you might also like one more than another, of course. Anyways.
You can compare two genres, not easily though imo. Its different if you compare Classical music to Rap music.
Also I didn't really get you there at the 'no music is perfectly defined by genre.' Damn im going stupid