Suppose you control Empyrial Archangel and a planeswalker, and a source controlled by an opponent would deal noncombat damage to you. Both Empyrial Archangel and the planeswalker have effects that change (or could change) what that damage would be dealt to. You choose one to apply. -- If you apply Empyrial Archangel's effect, the damage is redirected to it. The planeswalker replacement effect is no longer applicable. -- If you apply the planeswalker replacement effect, your opponent then chooses whether he or she wants to redirect the damage to your planeswalker. If your opponent does, that many loyalty counters are removed from the it. If your opponent doesn't, then Empyrial Archangel's effect applies and the damage is redirected to it.