Provided the installation has been done properly, the Rotax should do better in the longer term than any comparable horsepower air-cooled engine operated continuously in hot weather.
I have no experience of the Tecnam, but looked at two different models today, the retractable and the fixed gear two seaters. The engineering looks good and it seems solidly constructed with decent weight in the skin and frames, unlike many light aircraft in that category. My gut feel (and that's all it can be until I fly one in a week or two) is that it will be great aeroplane for the Australian bush environment. But it's relatively expensive.