wish I went to macrob 
for the ladies?
-unlikely
Your SAC marks will scale highly in subjects with very large cohorts (80+), but you should be a bit cautious in the smaller subjects where if some of the top rank students screw up their exams then the rest of the class suffers.
If you outrank everyone in your class their scores can not bring you down. The downside of smaller subjects at selective schools like MHS and MacRob is that when there are only 15 kids in a class, there are still going to be very smart people that beat you on SACs through the year, and if you have a look at what happened in some of the humanities subjects last year where the #1 ranks got SS of 39-42, the rest of the class got dragged down getting lower SAC scores than their exam mark (pretty rare at selective schools).
So yes, if you do big subjects like Chem Physics Accounting Maths English or Psych etc, MacRob is the far better choice.
Additional benefit is that you get to hang out with Melbourne High guys who are all very cool.