As people have said, it really depends what you like. If you are an outdoorsy person who likes sport (i.e a bit of a 'jock') then Australia is perfect. The personal space also appeals to me. The thing I hate most about the UK is the overcrowding. There are too many people jammed onto this small island. Also, the houses are too small, squashed together, and overpriced. Light and space - those are the best things about Oz compared to Britain.
But I find the UK a far more interesting place than Australia. Intellectually, it is one of the most stimulating places on earth. For example, I remember wandering around Oxford last October and saying to a friend "there is literally nowhere on earth I would rather be." Over that weekend, we saw the pub in which Tolkien and C S Lewis used to drink, the college where Oscar Wilde was a student, and then the Ashmolean Museum (one of the most amazing buildings I have ever visited). I get such a thrill when I walk around Oxford or Cambridge. Just thinking of the people who lived and studied there, from Darwin and Newton to Stephen Hawking and W H Auden and Wittgenstein and Nabokov, and so on. Then there is Bath, with its Jane Austen connections, or the Moors, where the Brontes wrote, or the Lake District where Wordsworth lived, etc. Not to mention Glastonbury, or Shakespeare's Stratford, or the Cavern club in Liverpool. And that's before you even get to London. Bill Bryson writes about this - the layers and layers of culture and history you can plug into.
It's a shame that we take so little pride in our literature and cultural history. It's the best thing about living in the UK (compensation for the grey skies and lack of space). I'm sick of smug, woke bullies sneering at Britain's past and doing all they can to make us reject it. In my experience, Aussies, Americans, Indians, Canadians, and so on, appreciate our history and culture far more than we do. Personally, I'd like to kick out every sneering British woke bully and replace them with Australian and North American anglophiles.
As for the weather. Well, yes, I hate the UK in November and December, but this summer has really shaken me. I came down with heatstroke at one point - literally vomiting and passing out. I utterly loathe the heat and cannot wait for Autumn.