Hi sl138!
I'm going to be honest, I don't know much about Griffith and USC. However, I have looked into UQ quite a bit as that is where I will be going this year (I won't be studying medicine however).
Generally, UQ ranks highly when it comes to medicine and science. For medicine, the Herston and St Lucia campuses are both great, but it really depends on what aspect of medicine that you want to study.
Herston: in close proximity to major hospitals such as the Royal Brisbane and Women's Hospital and is also close to the QIMR Berghofer Medical Research Institute. This means that UQ students work closely with and have access to leading health researchers, academics and professionals.
St Lucia: home to the Queensland Brain Institute - so if you are interested in studying the brain, St Lucia is great. Personally, I have been to the QBI and the facilities are incredible. That being said, I haven't been to any other brain institutes to draw any comparisons - nevertheless, it was very impressive.
UQ is definitely great for research; a lot of post-grad students choose UQ for its facilities, so it is very capable of supporting further study. It is one of the
Group of Eight universities in Australia, meaning it is one of Australia's research-intensive universities. Additionally, Go8 universities have a focus on "international alliances and research partnerships." UQ is well-known and well-regarded internationally, which may definitely help provide more opportunities for research abroad.
That being said, Griffith is a fantastic uni - very underrated. I would say, if you are looking for a more hands-on approach to learning, Griffith is great. UQ is more theory based and Griffith is more practical. The GC campus has a University Hospital which is fantastic, however UQ has more ties to major hospitals.
I really don't know anything about USC, so I can't really provide any perspective on that. But I know lots of people who went to Griffith and the quality of knowledge that students gain from Griffith is amazing. I think that speaks volumes about the quality of teaching. Further, Griffith generally has smaller cohort sizes than UQ, so you get a more personalised university experience. I have heard that for your first year at UQ you can feel more like a number than an actual person, but, other than that, I've heard lots of great things about the student experience at both universities.
When it comes to ordering your preferences, make sure you place them in order of what you want to get into the most (pretty much ignore that ATAR requirement). You will get one offer per offer round, and they will give you an offer for your highest eligible course. So, for example, lets say you really want to get into course A which has an ATAR requirement of 80, but you also put down course B which has an ATAR requirement of 96. If course A is the course that you definitely want to get into, put A down as first preference. If you order them based on the ATAR requirement, an you get an ATAR above 96, then you may get an offer for course B and not course A. So, put the one you are most interested in first.
I would suggest going to the open days this year to see if you can find out any information that will help you make a decision on what uni is right for you