The AUD is traded as a commodity currency, and also as a free-floating barometer of bullish/bearish sentiments about China.
RBA cash rate are below 1% and signaled to fall further.
The Euro has serious underlying issues, like negative interest rates.
Hard Brexit is a near-certainty (which might actually be bullish for Euros) and Italy's government (makes Greece's government looks responsible) is close to collapse.
However it is a much larger diversified economic base, the has accumulated a lot more capital. The ECB is far better prepared to weather the coming storm.
If push comes to shove: I'd rather be holding Euros than Aussie Dollars if the goal is value preservation using the USD as a benchmark.