The slight differences in ATC-pie are:
- you can "ignore" radar contacts (similar to OpenRadar's "neglect"), they will turn into a faint "X" on the screen
- ATCs are not radar contacts, they are invisible (not neglected), but listed in the ATC list for handover strip drop
- you can also "blacklist" a callsign, to filter out their text messages completely
E.g. for pilots to know where and when to expect ATC service when planning a long route.
ATC-pie offers a way to do it from the system menu, without logging into Lenny's site and filling the location details. You can always edit your session there afterwards.
[EDIT: too much quoted from RubengamesenvlogNL]