I usually prefer to eat the elite complimentary breakfast in the restaurant if given a choice. Usually wider variety and less wait, and often less crowded. That wasn't quite the case in the Marriott Buenos Aires, but still good.
What's not good is some US (especially Hawaii) hotels give $10 FB credit for breakfast (Marriott Waikiki, or Westin San Diego) or muffin/yogurt/coffee for breakfast.