I use it in this way:
"Preserve scale while changing chart" is ON
This is my normal setting where I can view details on small charts
from "above" and if I like I use a zoom function to fill the screen
and then lose the overview if it's convenient for the moment.
"Preserve scale while changing chart" is OFF
When I sail in narrow waters and like to have one mouse click to details in front of me and only one click back to overview. I then use the "Chart Selection Bar".
So I do agree to Pavel's opinion. I use both options but do like to have the possibility to choose.
Just another tip for detailed/overview screen
. I use a second portable instance of O for overview. See my screenshot. (A VDR play. Never been "over there".