I have been to both countries, here's what I think.

Weather-wise, Australia is hot, Canada is cold.  Of course, I am generalizing.  You could live in Vancouver and it rarely snows there.  Similarly some parts of Australia never go above 35 degrees celsius.  If you love winter sports go to Canada.  If you love summer sports, going to the beach, definitely Australia is for you.

It's true that Canada, particularly Vancouver, has been consistently rated as one of the best places to live.  It's just beautiful over there.  But come to the eastern side of Rocky Mountains, Canada is flat and some would even say ugly.

Melbourne, Australia has been rated as #1 city to live in recent years, surpassing Vancouver.  But I do not think the former is as pretty as the latter.

Australia has higher number of Nepalis than Canada, I hear.

The minimum wage is higher in Australia, $15 vs. $6.  Currency is almost of same value viz-a-viz US Dollar, CAD is a shade higher than AUD.

I guess it really depends where your friends and family are.  I personally prefer Australia, but that's just me.