I think everyone's circumstances is different and you have to constantly check & call around for a few quotes at renewal time. If Bingle is the cheapest for one person, it may be more expensive for another.

Age, gender, location car is garaged etc all play a factor. I think the companies have different data & use different formulas to calculate premiums.

For me, personally Allianz was the cheapest ($720) compared to Bingle, NRMA, CommInsure, GIO, AAMI, and VW's Allianz policy (which the VW insurance person wasn't too happy about).