I only have a Galaxy S but this being the Internet I still have an opinion
First off I don't know how the prices of new iPhones (4 or 4s) and Galaxies (S II) are in Australia, so I'll assume they're about the same. If one of them is considerably cheaper with comparable phone contracts it's probably not worth paying much more for the other one.
If you just want to use the Phone and are happy with the walled garden Apple provides I'd go with the iPhone. They still seem to provide the best easy to use experience. Also many companies still seem to release an iOS app first and Android later if at all.
If you'd like to be able to tinker with your Phone a bit (or much if you prefer) more then Android is the way to go. There's plenty of ROM's you can choose to use that offer more/different functions than the standard firmware provided by the manufacturers, xdadevelopers
is a great side to read up on that.
You also have the ability to use other Appstores besides Google's Market, so you're not restricted to Apps Google approves of.
On Android there sure are many (free) Apps for almost everything so it's unlikely you'll really miss something that's available for iPhones. But I think that there are still more (good, but not necessary free) games for the iPhone, though I have to admit I'm not that interested in games besides the occasional puzzle/match three game to pass some waiting time.