They are very different.
Psychologists listen and talk a lot. They help patients by allowing them to think differently and as a result behave and feel different. The reverse is also applicable ie. psychologists can teach patients new ways of doing things, and by doing things differently, the person gradually starts to feel and think differently. This is called cognitive behavioral therapy. Psychology has a lot to do with trying to understand what people are thinking and how to make adjustments.
Physiotherapy involves Anatomy and Physiology. Anatomy of physiotherapy is mainly to do with bone and muscle. In terms of physiology, you will be learning about how the body works eg. how do all your organs work together as a team to keep you alive; what happens when you exercise, how does you body put up with all the extra demands. You will be using your hands a lot, not necessarily to massage, but to mechanical advantage to help people improve their physical status be it rehabilitation or preparation for a final competition. You will also listen to people and explain things to them, but not digging so deep into their mind like psychologists. You will be focusing on muscle and bone.
Physiotherapy is more science. Psychology is more art.
Best way to find out is go shadow a psychologists and a physiotherapist. People of both profession are generally very nice and approachable. For privacy reasons you may find it hard to sit in with a psychologist, but talk to your career advisor see if something can be organised. Alternatively there must be plenty of videos online on what a psychotherapy session is like.
In terms of career prospect, both Physiotherapy and Psychology are in demand. You won't have trouble finding a job in Australia.
(A side point: If you are interested in Medicine, or might be interested in the future, there is one advantage about physiotherapy over psychology: People who finish physiotherapy, have a big advantage when they then go study Medicine because you would already have half of Anatomy and Physiology covered. Certainly Psychology will also help with studying Medicine but not as dramatically as Physiotherapy)
