If the damage were only slight, as you suggest, I would think it would be better to have it repaired before you advertise it. It would certainly make it more attractive to a potential purchaser.

Generally it was always felt that the air-conditioning of European cars wasn’t up to the task for Australia; that was because there wasn’t the demand for powerful A/C in Europe where the climate is generally milder. But when the European carmakers began to move on to the world market and export their cars to places like America where the demand for good A/C is very high they have improved the performance of the A/C systems in their cars. The cars you say have had good air are cars that are typically built for the US market, those you say don’t have good performance are not. A/C systems soak up quite a bit of engine power in driving the compressor and that has a greater impact on smaller engines than big ones, and again the cars you are critical of have smaller engines, so they will also probably run smaller compressors.