Harris is way bigger and much stronger, he took down Mayhem down pretty easily. Paul Harris has a pretty good chin as well, Nate had like a free shot straight to his face and still he didn't knock him out cold. Other than that one incident he hasn't been TKO'ed or KO'ed. For 3 straight rounds there is no way that Paul Harris can't take down Bisping once. Once the fight hits the ground Paul Harris is just going to wreck Bisping. 2nd round submission probably Kneebar or Armbar.
Bisping wouldnt TKO him , he would most likley stick and move and jab to a points win. Bisping has great cardio and isnt easily taken down , if he is down then Paul harris wins if not he wins that simple.