I don't know about Marriotts but Hilton vs Hyatt comparison is like night and day. Hyatt diamond desk is staffed by some of the most accommodating and customer friendly folks (in my 3-4 yrs of diamond not once i was left with an unresolved issue including numerous rule bending and "exceptions" in my favor) and Hyatt board had several active company reps who quickly resolve any issues once you PM them.

My recent encounters with Hilton diamond desk on the other hand resulted in "i can't help you" as i tracked budget bonus points, "it's for your own benefit" when i expressed concerns about upcoming diamond force limitations, and an erroneously cancelled reward reservation (which took another hour on the phone with a supervisor to restore) when i asked them to add a request for two cribs in my room.

There is no comparison.