Would normally agree with you Penguin (especially as it will favor the Reds) but the issue in Super XV is that not every team plays every other team or even the same teams as the teams in their conference.
Check out the teams the Brumbies have avoided playing this year.
No perfect method in this situation.
But those draw inequities apply to both methods. Wins are still a better determinant than the for-and-against difference.
You can see cheap points racked up after a result is all but sewn up, where a dominant side takes the foot off the gas (e.g. Brumbies-Force, or Bulls-Cheetahs two days ago) - or where a side gets blown out after unlucky injuries (e.g. Reds v Sharks). It's a minor thing because
any larger differential can be trumped by 1 extra point on the ladder.
By contrast, cheap wins rare. Large wins are clearcut and deserved. Narrow wins can be lucky, but you still have to be close enough to the oppo on the day to get the upset. You have to put in to get those 4 ladder points from close wins.
Wins and losses are where it's at. Differentials....... not so much.