Hi Russell,
The lower you go, until the ESC refuses to govern any longer, the tighter and faster the RPM control loop can run.
I have always been an advocate of running with more "voltage overhead" for better control when maneuvers place a large transient load on the prop/motor combo.
The downside is additional ESC heating, but this is easy to check: if the ESC ain't too hot then all is well.
Regards,
Dean Pappas