I'm Gold with Marriott, Diamond with Hilton, and also own HGVC property in Honolulu. With all that, I far too frequently get the room with two short-sheeted double beds next to the elevator, across from the ice machine, and no recognition of my loyalty to either brand.
Most clerks and front desk managers do not look at pending check ins by elite members when they start assigning rooms, and even if they do, the whiny tourist who checks in at noon will bump most elites every time. Your room "requests" are not guaranteed by any hotel chain when it gets down to the individual property level.
I personally don't care about breakfast, and I have more points than I care to use, so the only benefit of a loyalty program for me is in the recognition and upgrades it affords me each time I give a hotel my business. In fact forget the upgrade... just guarantee my reservation and don't downgrade me. I'll make it simple for you.