I started the thread linked in the above post. I am currently studying at UNSW and I would say that it doesn't matter which one you pick. You cannot possibly go wrong with either. Both are great law schools.
Things I would consider if I had to choose again includes:
1) travelling
2) what degree am I combining it with? Typically Com/Law I would pick UNSW and Arts/Law I would pick USYD
3) your perception of the uni in general
4) student societies that you can get involve with
5) exchange opportunities (realistic ones). E.g. if there is only 1 exchange spot to harvard, do you honestly think you will get that spot???
6) law extra-curricular opportunities e.g. mooting
I am sure there are more things to consider but for now that's all I can think of