hi frozzie,
basically it is a call on investing in your unit versus shares, so many of the basic pro/cons lists shares vs property will be applicable. Yes shares are more volatile, but far better diversified, liquid and lower in transactional costs than property. Some of the volatility is apparent, since your property price does not fluctuate every minute in front of your eyes as shares do. Property is also much more hands on, dealing with tenant issues or at minimum a property manager if you can be lucky enough to find a good one. Shares you can be as hands on (active) or passive as you choose. Many Aussies tend to be well overweight property owning their own home plus investment properties, in which case I would suggest shares. In your case you will be renting so this would be the only property investment, so it is not too heavy into property compared to the norm here. I don't know much about Sydney property so won't comment on that.
I invested a lot in property through my life, but if I had my time over I would choose shares, as you can probably tell by the above paragraph. The political tax debate is also quite interesting at the moment, and depending on how it ends up might have implications for the attractiveness of shares vs property, so that is also something to monitor.