Masters degrees generally require a more rigorous study program, which may or may not have more emphasis on research than the bachelor degrees. In the case for nursing, it appears from the unit of study table that there is some degree of research involved.
It is important to remember that ATAR cut offs are generally indicative of demand, not the quality of the course per se. For what it's worth, while the Advanced Studies cut off is slightly higher, last year there were vacancies after the Main Round. For two of the three combined programs however, there were not. This would suggest that many of the people getting into the Advanced Studies degree in a later round would have an ATAR that could be well less than that of anyone who had been admitted into the Masters program (this is of course not taking into account access schemes or bonus points). But again, I don't think this is too relevant. What would be important is the quality and the content of the degrees themselves. Doing some research on the university websites and handbooks should provide you with the information you need.
With that considered, I would recommend doing the Combined Masters degree over the Advanced Studies program. You get a more holistic, flexible education (in health science/science in general, not just nursing), and you would also finish with a Masters, which is a higher qualification.
