Meeting load being the deciding variable matches mine exactly, and there is a check you can run before committing.
Export both calendars for a typical month and overlay them. Not to see conflicts, but to count how many hours are genuinely uninterrupted. If it is under about four a day, there is no room and no amount of discipline creates any.
The second thing that check reveals is whose meetings move. A role where you can decline a recurring invitation without anyone noticing is a completely different proposition from one where you cannot.