sydney and unsw are pretty even as far as commerce goes, I can look at this objectively even though I am a Sydney Uni student.
It depends on what suits you, Minai told a bit of a furfy when he said that the commerce degree at UNSW is flexible, at Sydney you can major anywhere else outside the faculty within a commerce degree as long as you have one commerce major in your degree. So you could major in marketing say and chinese or accounting and ancient history, its up to you.
Just talking about faculties in general, the economics and business faculty at Usyd offers many more degree programs also to suit individual needs.
e.g. Commerce, Economics, EcoSocSci, Commerce (liberal studies)
For me Syd was the choice because for what I want to get into (that being the high end finance industry, investment banks in particular) dont think about going anywhere other than UNSW or Usyd you wont get hired, they campus recruit from syd and UNSW only - cry the big four go to all the campuses, yes I know they do but im not talking accounting firms here.
I am in liberal studies variant of Commerce more or less because its commerce/arts in four years rather than 5, usyd had more degrees and met my needs because of that.
Also I think you will find that Sydney University is MUCH MUCH more respected internationaly and held in a higher regard overseas - go to wall st., hey you ever heard of sydney uni or UNSW no, but hey they are sure as hell more likely to have heard of the Uni of Sydney over NSW.
Take into account the sydney uni social scene and the demographic of the "type" of students who attend Usyd and you have yourselves a winner, plus why would you want to go to a glorified tafe college coz no offence UNSW ppl at the end of the day thats what you were and really what you will always stay.
Dont take it too personally =) love the Usyd Unsw rivalry