Actually, neither. I have no explanation, but it saved my behind on a HUGE install. I couldnt get the status light on an mrf-250 to vanish so i plugged straight into the wall. Interference gone!!?!?!?
I was baffled so i tested and retested, and sure enough that was it.
Oh yea, i usually place the mrf's at the lowest point of the cabinet or equipment rack, that seems to also help with interference.