Monash is still quite 'prestige' in my opinion. I say that in comparision to Latrobe and Deakin, so your future prospects are still quite 'good'.
I would prefer the Melbourne if you were confident enough to be able to handle the work put into 1-3 years of an undergraduate course to get the scores required for an interview. Further, Melbourne has the LSAT - let's not forget - definitely a potential barrier. For a course demanding and competitive as law, many employers like the prestige of the university due to liasons and experience with the alumni. In addition to this, perhaps the course structure is favoured.
Personally, I would do the undergraduate at ANU. It has a nice course structure, which is quite intimate allowing the student to develop a relationship with professors and tutors. However others learn in different ways. I believe if you really want to do your course and are able to select where you want to go, then look at the course structures and do your research to find the university that suits you.