My limited data points at full service properties in the US in the last two weeks: 2 Hyatt (globalist), 2 Marriott (plat), 1 Hilton (diamond). I was able to do a full service breakfast at all of the Marriott and Hyatt properties. Did ok at the Hilton because I added a second name to my solo stay, and had enough credit at that point to order room service for one person.
Overall though, the recent Hilton breakfast change has moved it to the back of the pack IMO. It seems to me that the breakfast benefit is doing much better at Hyatt and Marriott compared to Hilton, but it varies by specific hotel.