Opps, I didn't read your question properly. I picked UNSW because:
For the science degree, UNSW is more flexible. In USyd, they would have made me do Physics, 2 semester of maths. In UNSW, I only have to do 1 semester of maths and no physics at all if you don't want to. Plus 3 electives for UNSW first year.
I like the campus better, which of course, is an individual opinion.
Bascially both uni offer advanced level or normal level subjects so it's the same. Really if you don't care about doing physics or maths and the campus is similar to you, then it's really a flip of a coin which uni you should go!