GF I lived in Melbourne for 18 months (had 4 year visa) 5 years ago, I can honestly say it's very nearly 6 of 1 and half a dozen of another. We moved home because life in the UK is better (I know you won’t believe me!) We had a private white sand beach less than 50M from our house, it was nice, but not as nice as you think it would be weirdly. Whatever you have you will take for granted in which ever country you chose, personally I wouldn't go back but I would live somewhere else in the world for the experience. I would also add there are a lot of negatives that you will never know unless you go there and live the life, you won't see this if you go on holiday there, it isn't all about the sun and I did notice this was at the top of your list.
Here are a few positives for you:
New Years Eve at the height of summer is amazing, we went swimming in the sea fully clothed when we got home around 8am, wow!
Earning pounds at home (renting) and then turning them in to oz dollars is impressive, it gives you good purchasing power as I'm sure you know.
You could have a very big modern property on the sea front with huge open windows looking over the sea for £150,000 when we were there.
I have always said if I ever become single again I will go back because the ozzie girls are very forthcoming!
Didn't see any snakes
Fantastic coast line
Here are a few negatives for you:
Every property has a redback (not too bad) but white tails seemed to be everywhere, 2-3 a week in our house and they are a problem, worst case scenario amputation.
Oz has a massive hole in it's ozone layer, it is skin cancer city
The food is generally poor from supermarkets and not great from specialist shops, restaurants were fantastic.
You cannot speed there or park illegally, we had a ticket at 00:20 on a Sunday night in the CBD, they are on commission. I also had at least 1 speeding fine every week.
(Thankfully on an international licence they can't ban you, just earn enough to pay the fines.

)
The Ozzies are very American, I much prefered the South Africans and the Kiwis.
Christmas in the middle of summer, WTF it's horrible.
The Ozzies seem to confuse being relaxed with laziness, I worked much harder than my colleagues.
I've had to stop myself I was starting to go in to one, but you can see the -'ives for me at least out weigh the +'ives. I would still think about it if the opportunity presented itself again, but I know my answer would be no in the long term. I took a £15K pay cut with diminished responsibility in my job to come back to England, I am still happy with my decision.
One final comment, I would say if you have young children don't go. Gang violence and white tails would be a real worry for me.
Good luck with your decision.