Selected is a bad idea because it defeats the whole purpose of groundspeed mini (which is a constant GROUNDSPEED approach).
The reason that was created is because the autothrottles are not fast enough for all conditions and cannot be "helped" out like you could in brand B... There are situations where the aircraft will completely unspool itself. Groundspeed mini guarantees you enough smash to survive it. Selected speed does not.
But manually running the throttles will allow you to pull em towards closed but not completely closed, so you are still spooled...
I will fly my 140ish approach speed instead of the 170 groundspeed mini is commanding and be ready with a whole handfull of throttle knowing that I got 30 knots that are about to disappear somewhere.
So the groundspeed mini depiction of target airspeed is not my target. My target is the 140 ish or so I am looking for. Groundspeed mini becomes my psychic advisor of whats about to happen. Airplane stays at a more or less constant airspeed. Much less trimming going on, engines always spooled etc...
Selected speed with autothrottles in use is just defeating a safety feature that airbus felt you had to have because of the way they designed the autothrottle system.
Cheers
Wino