It will all depend on what price you can get the flights for and the weight of your dog.
We had to do this 3 years ago with our two labs.
First thing is to get quotes from the pet shippers, ie Jetpets, Dogtainers, etc. This will let you know what price you need to better, then head onto the websites to price up flights to Sydney and back. Only Quantas and Virgin will allow your dog on so the return flight will need to be with one of them but you could use one of the cheaper airlines, Jetstar, tiger to get to Sydney .
your dog is calculated as luggage, so you only pay for anything over the luggage allowance. Our two combined weight came in over 80kg but it still worked v cheap.
You would need to check if you can use the crate that they were in to get here, if not you can hire crates cheaply and the company will bring to the airport for you.
You need to book your dog direct with the airline, no forms, just a phone call and you don't pay for the dog until you get to the airport, ie they weight them then tell you the exact amount, although you will already know roughly how much your dog weighs so will have a good idea.
So in the end it all depends on what comes in cheaper and if you want the hassle free route and not have to fly over yourself.
The other difference is if using a company then your pooch will fly on a cargo plane, obliviously if they fly with you then its on a passenger jet with you (still in the hold though)