All the points of sale listed here offer the same Swiss Travel Pass. The only slight difference is the way you start using (validate/activate) the pass: passes issued by the Swiss Railways can be validated by filling out the blank fields (name, passport number) yourself. The passes issued by Rail Europe need to be validated by rail personnel on a Swiss station or on board of a train bound for Switzerland. This is a one time process, so not a major difference. Since you live in Australia, both www.raileurope.com.au and www.raileurope-world.com make sense price wise. Also, Rail Europe currently offers a few additional discounts.
All you need to know about traveling by train, bus or car in Switzerland.
Hand picked Swiss hotels and other accommodations are right here.