If nobody knows which face has more chance to appear, the one who choose that face (by chance) has more chance to win, independently of the tossing.
If one (only one) of them knows which face has more chance to appear, he will bid that face and has more chance to win.
If both of them knows which face has more chance to appear, they will both bid that face and nobody will win.
If one (only one) of them knows which face has more chance to appear, he will bid that face and has more chance to win.
If both of them knows which face has more chance to appear, they will both bid that face and nobody will win.