Australia, New Zealand & the South Pacific - BBB equivalent in AUS?

I was wondering if there was a BBB equivalent in AUS as we have in the US.

Here's what I found so far:

http://www.fairtrading.nsw.gov.au/default.html
http://www.accc.gov.au/content/index.phtml/itemId/815215http://www.consumer.gov.au/html/faqs.htm#consumers

I am basically looking to rent a car in downtown Sydney and looking to see if there have been any issues with Europcar, Alamo, Budget, Avis, Hertz in downtown Sydney. The price quoted by Europcar and Alamo are much lesser than Avis/Hertz. What am I compromising on? What would you guys suggest?

There's nothing like that here. The ones you mention can have issues reported to, but don't have a searchable register of reports. They only issue specific announcements when they feel an issue warrants it.

As for the car companies the local majors are Hertz, Avis, Budget and one you've left out - Thrifty (which also tends to be cheaper). Europcar and Alamo have less of a presence here so that is probably why they are cheaper - less convenience/appeal. If you find a package you like and the location/terms suit that's probably your best indicator amongst that group though; there's no particular reason against any aside from what you see in pricing, location convenience and terms.