These are all opinions, nothing definitive (and I gather this is what you want coroneos)
USyd: Prestige (highest in Australia), sandstone, lower cutoff than UNSW, more local students (in commerce), new initiatives in accounting for example (refer to suvat)
UNSW: marginally better prospects (starting salary and employability), historically big4 firms hire more UNSW grads than any other uni, prestige of the degree itself, links with the asia-pacific region