The VMG is for light air conditions where the VMG (Velocity Made Good, i.e., the overall distance directly toward the downwind marker as measured by a rhumb line from upwind marker to the downwind marker) will be greater by choosing higher courses that keep boatspeed up, than a close to Dead Down Wind course; the RUN is for long, deep downwind courses when the wind is a bit stronger.
You may notice the VMG is cut a bit narrower across the belly, and can be flown closer to the bow, which makes handling all that yardage through all those downwind tacks a manageable chore. The RUN: well, that's just a big, fat spinnaker.
