For me to learn RPL, it would cost around $200 to $250 hour out of Parafield. With RAA, is around $135 with where I am doing this through.
Now there is quite a few differences between the 2 in regards to what you can do. ie RAA, you can not fly in controlled airspace, Max weight is 600KG, where as RPL is 1500KG Max weight and you can fly into controlled space. If you want to fly bigger aircraft, RPL to PPL is the way to go.
In terms of flying, I believe they are similar for the course structure and many of the endorsements / requirements are the same, ie VFR, aircraft control, radio, ect.
For me, I just wanted to get out and have fun without breaking the bank. If I chose RPL, I would most likely not do it because of the cost.
Not sure if you have seen this on the RA-Aus website: https://www.raa.asn.au/learn-to-fly/recreational-vs-private/
Also, if you want to convert to RPL later, it seems quite easy with minimal hours. See the RPL info here. http://www.casa.gov.au/wcmswr/_assets/main/lib100191/rr61_rpl_fs.pdf
It states:
I already hold a pilot certificate issued by RA-Aus. How do I obtain an RPL?
A pilot certificate is equivalent to an RPL. To get your RPL you need to complete an application form, and follow the instructions on the form to provide evidence of your pilot certificate, submit a recent photograph and provide appropriate proof of your identity. You also need to undertake a flight review before you can use your licence. Your new licence grants you the relevant category rating, aircraft class rating and design feature endorsements. You are also granted a recreational navigation endorsement if your pilot certificate authorises you to conduct crosscountry flights and if you meet the minimum flight times.