A true wing has more differential pressure, from the lee side to the windward side, than a soft sail. More pressure diff. = more lift = more drive = faster, as long as you can control it. The biggest issue is to sail it (or Fly it) without stalling it, which would create much more drag.
Yes, unlike an airplane wing it needs to tack and sail in two directions. Kind of like being able to fly and airplane upside down and right side up and change at a moments notice.
