Registration for Australia or New Zealand?

I have been qualified for 10 years from the UK and have been working overseas in a small British Protectorate for 4 years. I am now keen to work in Australia or New Zealand. I have been looking into both registration processes and it seems the New Zealand registration is the most straight forward despite having to provide a lot of paperwork. My main concern is that I have been working as a musculoskeletal physio now for the past 5/6 years so my evidence for respiratory and neuro disciplines seem very out dated. Will IST and reflections be acceptable from this period or is it worth me trying to do some work shadowing in these areas to help my application? I see from the guidance notes that evidences is accepted up to 10 years, would this apply to the Validation of Work History forms? I would very much appreciate any advice. Also is it straight forward to use registration from one country to work in the other through the Trans Tasmanian Mutual Agreement?