I think I can definitely say that there's less lightning on the left HD wall. You can tell by the way Marshall's face darkens as he looks toward the monitor vs directly to the camera. Also, when compared to Heather's.
Also, has anyone pointed out yet that the OCMs have only been standing on the right side of the wall since the YWT broadcast began and do not move to the left? It looks like they don't have a monitor on the right side to look at.