I can only offer my input for Dr. Du, as that is the only one I've attended.
Teaching style: Very fast paced, almost to the point where it's almost impossible for people who aren't as adept at mathematics (like me) to understand what he's talking about half the time. He also goes off-topic, which is the reason why we finish, on average, 20 minutes late. He also covers an overwhelming amount of content every lesson. There are no practice questions during class, you have to listen to him lecture and draw perfect circles for the whole two hours. There is, however, a test at the beginning of every lesson, which is designed to assess how well you understand the topic from the week before. Should you fail this test, you will have to stay back.
Quality of education: It's very hard to understand what he's talking about half the time. The examples he gives in class are also too easy, making it extremely difficult for us to do the hw. They don't even offer homework class anymore, which sucks. Speaking of the homework, it's 16 pages (for the A class), and is extremely time consuming. The homework is also graded each week, which is another way to make you feel bad if you haven't completed the hw.
HSC outcomes: Just go there and ask, they'll be more than happy to give you that booklet with their top students and marks. I've seen a lot of 99+ scores in the booklet thingy.
Overall: Good if you want to be challenged and are able to grasp mathematical concepts quickly. You should be relatively adept at maths to go, as it's pretty hard to understand what he's going on about, half the time. (for me anyway). If you're dedicated enough to do the hw (which takes ages to complete), I think it'd be pretty beneficial. He also focuses on proving and deriving things.
I didn't really like Dr. Du because of the sheer amount of hw he gave to us every week. He's not really good at explaining things, either, and doesn't give enough examples in class. Anyway, this is my two cents. I know quite a lot of people who really like Dr. Du... so yeah.
