“I'd point out that not everbody seems to be answering”
Maybe, but it is fun!
The Jabs seem to suffer from lots of small problems requiring £500 a go. The Rotax seem to just work. This is based on aircraft around my area but does seem to apply to all 5 Jab owners I know and 10 plus Rotax owners. When I asked PFA eng about engine reliability 5 years ago, the Rotax was the most reliable in the fleet and the Jab was well down, but I think the Jab has probably improved its QA since. The geared Rotax can produce much more power at takoff with a CS prop than a Jab can with a light wooden prop. A 80 hp Rotax will work in a Europa for example, but an 85hp Jab will not do the job.
Rod1