The consensus we've gotten from previous Brawls is that anonymous voting 1) Doesn't actually remain anonymous 2) Hurts the fun of the event, and 3)Harms discussion, which is something we're mandating this Brawl.
We will continue using the voting system of the previous Brawl while also enforcing discussion so that players must give ample, realistic reasoning for their choices. There is /no/ perfect voting system, but this one should create the least bias.