Hey all! I think the displayed speed for you if you’re flying or ATC should be in IAS.
Group flights:
I feel like in group flights you never know what speed the pilot ahead is at so you have to do many adjustments.
ATC:
It would give a better indication to the controller of your actual airspeed if you are told to maintain say 210kts. The controller can easily see you are maintaining that speed instead of looking at the ground speed conversion.