I think Blackhawk might be a special case with a moveable tail plane but I also think aft CG is preferred. When flying faster, the pitch attitude tends to be negative, presenting the aircraft obliquely to the flow (more draggy). Aft CG tends to raise the nose at equivalent speed. I've flown at least one type where you managed the location of the fuel towards the rear tanks to raise the nose a little in the cruise. The disadvantage might be that the aircraft is less stable at cruise speed meaning it's more work for you/AFCS possibly sapping energy/causing drag.