It is also important to note that ACER and UNSW do not recommend or endorse any commercially available courses offering LAT preparation. As mentioned above, The LAT is designed to assess a candidate's ability to generate their own ideas and express themselves through writing.
Regarding your initial question, you should consider your career aspirations, i.e. what do you intend to do in the professional world as a Bachelor of Laws graduate? USyd and UNSW are seen as having good law schools as well as programs, and high achieving Bachelor of Laws holders from both institutions are typically given the priority with respect to employment opportunities, particularly at the larger law firms. Of course, while favourable performance (results + GPA/WAM) throughout your time at university is important, work experience (typically through clerkships) is also encouraged and can assist you in further demonstrating your knowledge and skills to prospective employers, irrespective of the university that you choose to attend.
I hope this helps!