To answer the original question: It depends on where you are, what you're trying to achieve and who's watching!
Flying a variable speed approach to the numbers of a runway, then taxiing 1000m at a walking pace is pointless and expensive (unless your instructor asked you to) so a constant speed approach/air taxi/quick stop might be more fun and more appropriate.
Flying over forest into a small confined area requiring a near vertical descent from a high hover would obviously be much safer with a variable speed approach.
I'm guessing most flights are somewhere in between. It's a magic carpet so put it where you need it?