Why will the Cowboys win this game? Because they can't. Romo hurt. No defense. Lost 3 of last 4 games including blowing it against Giants a couple of weeks ago. Playing against the Giants in their stadium. About every media person in Dallas already counting the final game as a loss.
Therefore, they win (somehow).
But does it really make much difference for either the Giants or the Cowboys to win? Not much, unless you count bragging rights as NFC East champion. Just gives the winner the opportunity to get embarrassed by either the Packers or the Saints (if somehow they can even make it past Detroit).