I grew up in Adelaide (11 years), and now living in Sydney (15 years), so I have my own opinion on this.
Sydney have great beaches especially at Northern Beaches area. I avoid Eastern Suburbs beaches (Bondi/Coogee etc) like a plague. Adelaide beaches like Glenelg is great, and all those beaches along the coast from Semaphore to Sellick Beach are great and not crowded.
I noticed that Adelaide CBD is getting busier and busier over the last few years when I went back to Adelaide. These days Gouger Street is always packed on Friday/Saturday nights with lots of people at restaurants. No way that was the case in the 90s.
Anyone who is priced out of Sydney real estate can always move to Adelaide for a quality lifestyle for fraction of the cost. To me that is the biggest benefit. For example, if you are police, fireman, teachers, nurses (i.e. standard jobs where every state needs them anyway), you would earn a really average salary in Sydney and you would not be able to afford to buy anything in Sydney. Move to Adelaide (and get the same type of job) and voila you should be able to get something much easier.
Adelaide is really great to raise families, if you can find a job there. There is simply less pressure for average families to pay mortgage and raise kids there. There is no such thing as traffic jam in Adelaide, if you are using Sydney standards to compare with. The weather is in general pretty good, and no four season days like Melbourne at all.
I agree that Adelaide is "less exciting" as Sydney. But how many times do you need to see Sydney Harbour Bridge, or Opera House, or Bondi? How often do you need to shop at say Cartier, LV, or Miu Miu? Most average families doesn't need this at all, even they are all located in Sydney.
500k Budget? You can get a large selection of suburbs for houses (not units/townhouses) in Adelaide, and in many ways, you can get it 10 minutes drive from city. You can even buy small house at Rostrevor/Magill area which is zoned in to Norwood-Morialta high school, which is a very good public high school. Try doing this in Sydney right now, you would need to look at 2770 or Campbelltown area. Miles away from Sydney CBD. I am not even going to talk about quality of public (non-selective) schools there.
A lot of Sydneysiders who are on average jobs will be burdened with very heavy mortgage on their backs (which could one day break their back when IR rises) or have no hope to ever afford a house. Whilst I do feel sorry for them, they should seriously start looking at alternatives.
To me Adelaide is simply a great place to raise family for average joe. Any Sydneysiders who move there, would need to get used to not hearing about Rugby League but everything about the Crows (which I still follow and support, with Swannies close behind) and Power ...