The best source of that sort of information is the Federal Chamber of Automotive Industries (FCAI). You could also ask Ford and Holden.

A/C compressors mostly fail because of a lack of lubricant through a loss of refrigerant gas in the system. The gas carries the   lubricant that keeps the compressor and other system components alive. I can't recommend an alternative system that you could turn to for your car, instead I would have the system checked for leaks that might be causing a loss of refrigerant, make sure the system is fully gassed, and check it at least annually.

When it comes to buying old cars I tend to go with the car that is in the best condition and usually the one with the lower odo reading regardless of age. In your case that's the older car, but because it has done a lot less kays it is likely to give you a better run in the long term. Of course the dual-fuel ED will be cheaper to run, but it will take you a year or so to cover the extra $1000 you have to pay for it. The ED was little changed from the EB it replaced; it had better side impact protection and used environmentally friendly gas in the air-conditioning system.