Rather than the typical you go, I go of other Wargames Whores Blade 20,000 replicates the chaos of battle as players take it in Turns to Move or Engage with individual Warriors rather than their whole Warband.
Who goes first? Well the Warband with the highest Courage gets to choose which of the two Phases to assign priority to and thus act first in. In the other Phase the other Warband acts first.
Simple and fair, the watchwords of the game.