I was seriously considering this BA (Adv.) (Hons.) degree if I didn't get into Combined Law. If you're aiming for a first year transfer into Law, then i highly recommend you study a normal Arts degree. The BA (Adv.) (Hons.) skips the junior units and throws you straight into the senior units. This might be difficult for you because you're not used to learning university content, and the essays require critical thinking skills that are highly developed in year 1. Hence, your GPA might not be as high if you did a normal Arts degree. For transfers the difficulty of the course isn't taken into consideration...only the GPA (and ATAR).
If your intending to study a postgraduate course (JD for Law, DMD for Dent or MD/MBBS for Med), then the BA (Adv.) (Hons.), might be a good idea. Because you do the honours, the research is tremendous and this will definitely come into consideration for the JD, I think the USyd JD website said that competitive applicants will be those from research oriented courses.
Apart from this, I can't see much of a difference from studying a normal Arts degree. The BA (Adv.) (Hons.) certainly helps you accelerate postgraduate studies and possibly provides you with essential skills to excel in postgrad courses (especially research). Nevertheless, a normal Arts degree will still teach you the valuable skills for future study and the skills which are overwhelmingly useful for all future career options.