In my opinion, you have to look at where the person is living, because their opinion might be biased. For eg, someone living in Melb is gonna say something bad about Sydney, and vice versa. Not everyone can be objective about this topic.
As for me, my hometown is Perth, I'm now in Sydney and I've been to the other capitals/family in the other states. Weirdly, its usually cheaper to buy food and clothes in Sydney and Melbourne, than the other capitals.
Sydney: expensive to rent/buy but plenty of apartments to choose from (some other cities dont have enough of those), has the best public transport out of the lot, beautiful, very multicultural, bit humid but its not as bad as Bris. Some hate that its so busy, some love it. Its so big, there's always new things to discover.
Melbourne: Weather is bipolar or often 4 seasons in a day. Has best nightlife. Easy to get to many other cities from there.
Perth: Cheaper property (but atm it has the lowest vacancy rate of rentals so is that really better?), crap public transport if you're not near a trainline, yes it gets hot there, but its a dry heat so you don't really notice it until past 35C. Beautiful but boring. It feels a bit behind the eastern states, but thats not necessarily a bad thing.
Adelaide: Hot. Probably more boring than Perth. Its called the city of churches for a reason, enough said. Gay scene there is probably smaller than Perth's.
Brisbane: Very humid, more chance of encountering bogan types (aussie rednecks lol), public transport is being upgraded because they're hosting Olympics in a few years. My sister lives there, many people moved there during pandemic and a lot of it is overcrowded. Perth is more beautiful. To me, Brisbane's main appeal is that its close to other towns and etc. Nearby Sunshine Coast & Cairns are great but you wouldn't want to live in trashy Gold Coast.
Another thing to consider is that the bigger the gay scene, the more focused it is on hookups and harder to find a guy to settle down with.
Anyway thats my two cents. This map might help you
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