I know very little about the post-graduate program since they haven't really revealed anything to us yet:
1) Pathophysiology - for what we did, pathology was based around computer assisted learning for basic pathology (ex. Paget's, Cushing's etc.) and we have tutorials with tutors for specific things like oral anatomy, pathology, etc. but it's definitely not based around small group learning.
2) Don't know about sydney - you would be better off asking someone who's gone to both
3) Grading is based on the H1/H2a/H2b/H3/P/F model - which has no correlation with normal distribution. That being said, for most science classes the majority of the class sits at an H1/H2a level, but for dental subjects, around a H2b/H3 level.
4) OMFS is currently being remodelled into being run by the RACDS and not individual universities. From what I've heard, they're saying now you complete your dental degree (5 years or 4 years post-graduate) and then a medical degree (post-graduate 4 years) and apply in based on your RACDS exam results. Not sure which one would be a "better school" for OMFS considering that RACDS will run OMFS programs.
5) Research courses = mostly populational studies and only very few experimental studies since it's very hard to get results in the limited amount of time we have to do research. Not sure about paid RA work.
6) Melbourne's quiet but has apparently got better nightlife. If you want beaches - go Sydney. It is illegal anywhere to engage in public drinking to my knowledge.