This is a really tough question actually, and can only really be answered largely based on our individual personal experiences of living in a particular country etc.
I actually have a duel nationality, i am technically half english and half australian. I was born in England and have lived the majority of my life here, although i also have a lot of family living in australia and i have lived there for long periods of time at certain points in my life.
Australia is a really nice country to live in, from a day to day point of view, i think it has a better health system and education system, and many parts of australia are very prosperous- property prices are also generally a lot cheaper in australia than what they are other here in england.
It does have its big problems though like any other place to live in the world, it is had an increasing amount of natural disasters due to global warming, it has a lot of problems in aboriginal communities (mostly centreing around alcohol and drug abuse and problems with prostitution, paedophilia, abuse between married couples, employment problems etc), and problems with its wildlife and how people are destroying it etc.
But on the bright side, my visits to australia have always generally being pleasant. I also think people are generally friendlier and happier in australia, its very easy to meet new people in australia and i generally feel welcome when i visit places in australia, people seem to smile more and be more positive than people over here in England. Maybe its something to do with the weather?
But there are still reasons why i would choose to live in England as a country rather than Australia, even though australia has many positive aspects/points to it.
Most of the reasons i guess probably seem a bit silly to you guys- for example, australia's landscapes can be very bleak looking, just miles and miles of scrubland and desert, all parched and all the same. I always found while living there that after a while, i just started to really miss the vibrant flourishing greeness of Englands green countryside, i missed having more seasonal weather too.
And Englands wildlife is so much more cuddlier and friendlier than Australia's- living on the farm in England, the sort of wildlife you encounter tends to be along the lines of cute small birds like finches and sparrows, little harmless friendly bugs and insects, soft and elegant looking roe deer and cute little foxs full of character, cute little voles and rabbits etc.
But if you live on a farm in Australia, its wildlife is more along the lines of deadly spiders, snakes, bugs and insects, scorpions, angry red kangaroo's, koala's which look cuddly but that scratch and bite you to bits, crocadiles and deadly snakes lurking in the freshwaters, and deadly poisonus octopus and sea urchins and anemones and fish etc lurking in the sea. Its like everything will either bite you or run away from you or both, and everything seems to be poisonus or deadly in one way or another. You really do have to watch where you put your feet and hands when you're going about your day to day buinsess and you live in one of the more rural area's in particular.
