Essentially, both universities have very good business schools, meaning that, in terms of the quality of education, your friend is likely to be satisfied with his education whether he chooses to attend USyd or UNSW.
In making an informed decision, it is important for your friend to consider whether he wishes to study Economics as a major within a Bachelor of Commerce or study a Bachelor of Economics. Given the nature of the Bachelor of Economics, it is likely that majors within this degree (for instance, Econometrics) would offer more sophisticated knowledge and skills than an Economics major within a Bachelor of Commerce. In such a case, UNSW may offer more options compared to USyd, given that UNSW offers a Business Economics major as part of its Bachelor of Commerce, whereas USyd does not appear to offer an economics-related major within its Bachelor of Commerce. However, if your friend intends to study a Bachelor of Economics, then the initial suggestion will most likely apply, which is the reason that he should closely examine each major offered within the Bachelor of Economics at both universities and, based on this, decide which university appeals to him more.
The university that a candidate attended usually does not play a major role in whether they will be employed by a particular employer (an exception being the legal industry). Their employability depends on their level of knowledge in their field of study (which can be demonstrated through favourable university results), the set of skills that they possess as well as relevant experience (if applicable). If they successfully demonstrate these qualities, it is likely that they will find employment within a reasonable period of time, regardless of the university that they attended.
I hope this helps!