Unless the winner of each heat is judged on points, it is really a competition of how many friends each band brings on the night. It doesn't matter if your band is any good or not, it all depends on how many votes you get at the end of the night. Which, of course, depends on how many friends you bring to the gig.
Band #1: We have 100 friends and they are all coming to the battle of the bands gig.
Band #2: Well we have 102 friends, so we will win!