PAL is way better (for reasons listed).
You could say Australia probably got it because of its British origins (remember the Brits invented TV {J Logie Baird}, even if the Germans did much of the improvements and got it to a more commercial level).
But the main reason for the 50Hz would be that Australia has 50Hz power, like the UK, as opposed to the 60Hz supply in the US. In the early days, the slackest way to build things was to tie it to the very stable power supply frequency. (And with a given bandwidth, if you have a fixed vertical refresh (of 50Hz), you get to run more lines each cycle --- at a ratio of 60:50, ie 576:480).