If you pick the pistol first, seeing how Kaji got wrecked even after the block you either secure a good hit, or leaving your opponent in a bad spot.
One is lethal, and the other removes the strongest shield, which would allow you to secure a hit with the sword on the second round.
Of course i am more concerned with Kaiji being able to kill a man, or actually swinging a sword pass a shield, because those factors may make the sword the worse weapon he has.