He is asking for a comparison of "Baked Beans" and "Pork and Beans"... British to American systems.
Same thing in the end but labeled differently.
US Army system is the Aircraft Commander's Rank does not determine that status....a Warrant Officer can be the Aircraft Commander with a Colonel as the Pilot.
It was not unusual for me as a CW2 to fly as the AC with my Company Commander (CO) as my Pilot.
They did not fly often and we usually placed them with an Instructor Pilot (IP) or a very experienced AC.
One was so dangerous we actually set up a Duty Roster to determine who flew with him as we wished to share that wonderful experience.
I would imagine the Apache crews generally have the AC in the rear seat flying the Helicopter and the Pilot/Gunner in the front seat doing the Navigation, and working the weapon systems.