Generally speaking, the Australian School of Business is regarded as a better business school than the University of Sydney Business School. At the post-graduate level, AGSM > USYD Business and I don't think there is much dispute over that. However, you're at the undergraduate level so the reason you choose one business school over the other should be more or less determined by other factors such as location, major, scholarship, culture, etc.
For what it is worth, the ASB has a higher rank that USYD Business. Rankings, however, place a high emphasis on research output and when you look at the research institutes associated with each school, you'll see that those associated with ASB tend to have more research published in tier-1 journals.
Another consideration is whether or not you want to go on a study abroad program. If you choose to go on a business exchange, you'll see that ASB has much more prestigious business schools. From what I've heard, USYD Business is not offering Wharton as an exchange option for this semester, whereas ASB sends between four to eight students each year. ASB also offers Stern. Wharton and Stern are usually THE target schools of Wall Street placements, but now I'm going on a tangent. If you're interested in economics, you can even go to Cornell. Unfortunately, USYD does not currently offer those schools. USYD however, are in the middle of (?) or have already gone through a very rigious curriculum change. It's designed to be a lot more innovative amongst other things. Just like how ASB offers better business exchange options, if you were doing say for example a combined degree with Arts, Law or whatever, USYD offers law exchanges to Cornell, NYU, Duke, Harvard etc.
At the end of the day, most people associate ASB as the better B-School because of its industry links. USYD is incorporating this into their program, but is really nowhere near how far ASB has come with its industry placements. The other main point is that there are more business electives/options/majors and a media report also indicated that the ASB had the most academics from foreign institutions.
But, it's what you put in to your university life that will make it better than the other. If you prefer USYD because of its cultural life, societies and what not, USYD should be the university to go to. Although it might seem like UNSW has a more favourable opinion, what will count are the marks you attain and the extra-curricula activities you engage in. For exchange, only those with WAMs in the HD range will get to go to institutions like Wharton so unless you're one of them, go to the place you feel that you are more comfortable.
When you look for a job, most recruiters wont differentiate between USYD/UNSW. Some will however, because it is their alma mater. But that's life and just a luck of the draw. Other than that, graduating from either of the two universities shoudl yield the same opportunities.
