Attended Mac.rob, I didn't really like too many of the teachers that much there (most were fine but I hated one in particular because she insulted me and made a bunch of assumptions about my life), I do think though that most of the posts in thread are over reactions and exaggerations. It's true that most teachers are not particularly great (although there are a few that were genuinely amazing, fostered a love for the subject and challenged you), but people have very high expectations of teachers in these schools as a result may exaggerate the 'terribleness' when they are not up to their standards. I find this attitude somewhat elitist and problematic, as while I believe that public schools deserved teachers of a better standard, many people seem to think that selective schools are entitled to better teachers than other public schools. I can literally assure that the overall standard of teaching is no worse than other public schools.
In terms of extra-curriculars and personal development (Mac.rob has only started to put an emphasis on it), the school is second to none. You do really meet a few amazing people in every year level who are very passionate about music, sport , drama, social issues amongst other things in an inspiring and infectious kind of way. Those are the people that changes your outlook, worldview and challenges you to be more socially aware. Obviously, these types of people exist in every school, but I think that Mac.rob/MHS makes it socially acceptable to be weirdly passionate about specific interests or to have strong views about social issues compared to many others. In addition, the alumni networks of both schools are very vast, and you are bound to come across a few people who makes the most out of opportunities out there and are really making the world a better place. Although most people do have opportunities in life, not many other schools really encourage of push students to take advantage of them (Mac.rob is still somewhat behind MHS there), instead usually saying just finish high school, complete a degree, do a conventional job (I would consider an average doctor and lawyer in that category too). I'm not saying that the majority of students/alumni are doing inspiring things, but there are quite a few that do, those are the type of people who makes you believe it's possible to do something beyond and strive for that.
Whichever way you choose, don't inherit the 'grass is greener on the other side' attitude. It's ok to go to MHS and leave the school, but do so because it's not right for you or are not enjoying it there, rather than because there are potentially better options.