The answer to your question is "it depends".
Everywhere in Australia is getting fucked by apartments, urban sprawl, development, and as such heat saturation in areas is becoming a real thing.
Depends if you want to buy, or are happy to rent. Depends on your budget, and lifestyle, and also where you are working. Too many factors to give a clearly defined answer.
it's between Perth or Queensland. Sydney to expensive Melbourne to cold Adelaide fuck no Tasmania to many banjos Darwin didn't make the list.
Perth - I know of someone that works in the mines in middle of WA. 2 weeks on, 1 week off. In his week off he could have chosen to rent and live in Perth, but instead flies back to Sydney to live at his parents place.
Time difference can be a massive pain in the arse, likewise being 6 hours in a plane from other states. Very isolated state if you don't have family and friends there.
Queensland - highly depends on where abouts. Cyclones, crocs, rain and rain and rain and rain. Floods and storms galore.
Sydney - Depends what your expectations are. Yes there are shithole areas (like every state) and yes there are areas fucked by development and apartments. I love it here though. Beaches not too far (even from NW Sydney), National Parks and bushwalks in close proximity, and then there's a harbour like no other, and a CBD that isn't too bad to work around.
Traffic is fucked regardless what state you live in.
Remember that Sydney is the oldest CBD of any state, and hence other states learned from Sydney CBD's issues.
a house close to the beach that doesn't have a mortgage for more than 60 years
Unless you go regional, anywhere near the beach you are going to get reamed on pricing as "everyone wants to be there". Just remember though that living right on a beach isn't great for cars.
Sunshine Coast brother, fuck Sydney. I will move the first chance I get.
Don't get fooled by Qld's SC. Got close family friends that live up there. Property investment spruikers pushed areas like Peregian Springs, Bli Bli (etc etc) really hard.
As a result they've turned areas of Sunshine Coast into the same shitfest that the NSW Central Coast currently deals with (just with added massive storms).
You can go from highest socio ecomonic multi million dollar waterfront homes in Noosa/Noosa Heads, to lower socio economic government housing/cheap as hell rents in oversupplied investment properties, REAL FAST.