The https://www.flyertalk.com/forum/marr...worldwide.html sticky thread lists out the general breakfast benefits per chain. It also breaks out how each hotel within the Marriott system offers breakfast within its lounge (if it has one) or if the lounge is closed or there is no lounge, what level/type of breakfast that hotel offers.

There is also the https://www.flyertalk.com/forum/marr...explained.html thread which offers a discussion around the general breakfast benefit for elites.

I'm closing this thread as further discussion can occur in one of the above existing threads.