I cannot comment on the schools themselves as it is many years since I had anything to do with flying training in Australia but purely on a location basis it is a no-brainer (for me anyhow).
Bankstown is in the Western Suburbs of Sydney and is (or certainly was) a very busy GA airport with more runways than I was entirely happy with and I found it all a bit confusing - I did my FW IR there. I stayed in a scruffy motel next to the airport and was more than happy when the course was over.
The Sunshine Coast is a very different proposition and is a very pleasant part of Australia with beautiful beaches, great food and a very laid back lifestyle. Both Caloundra and Maroochtdore airports are (or again - were) nice airports and close to everything.
Don't expect Australia to be a cheap option anymore though as the Aussie dollar is still very strong and prices for many things are comparable with the UK on a £ for $ basis.
Whatever you decide I am sure it will be a pleasant experience and you will be well looked after.