What is the best public school out there? The best school would obviously be the one that fulfilled its role as a school better than all the others, and the primary role of a school being to educate, I think that should be the primary consideration in answering these questions.
On the basis of HSC results alone, I'd say Ruse. But then, I've been subject to the learning atmosphere at Ruse, where it's increasingly developing into a situation where the validity and importance of an idea is determined based on whether or not the idea is among those points we all aim to frantically memorise so we can regurgitate and forget them; which, in a nutshell, is what the HSC rewards. From my contact with students and ex-students of the schools that regularly top the HSC lists, I can safely say that these schools are adapting at an alarming pace to a system in which education is an appendage to exams.
So which school is the best really comes down to your own definition of education, and in most cases, the judgement cannot be made unless one has experienced the learning (or lack therof) environment at every school which one is trying to judge.
To summarise: Good luck figuring it out.