I have a friend with a 3300 Jabiru, he operates it carefully - but after one long taxiing session it still dropped three valve seats. This is after various misfiring and generating issues. Would be a good engine - if they actually engineered it properly and did not fiddle about. I know a guy with the original 80hp - who had no problems until he fitted the Jabiru 'economy' jets and then promptly had a partial seizure.....
But the 912ULS is a very expensive engine. I have to say I love mine, I finally have an aircraft engine which requires only servicing, no routine replacement of worn out or badly engineered parts. The only downside is that it is frankly grossly over priced. I've looked at the 912iS and it is a very complicated 'solution'. The complexity is as yet unproven in terms of reliability and in the last couple of years it has become apparent that Rotax quality control is little better than Lycoming or Continental - so much for certification.
On that basis I would not go for the 912iS. If there are issues then the Rotax warranty is less than generous and their approach to claims is difficult. The ULS is a pretty good engine if operated carefully and serviced as it should be. The ability to fault find the iS is going to be much less widespread and require equipment that individual owners are unlikely to be able to afford. If the iS systems had 5 years of faultless service I would plump for them immediately - but they do not and even Rotax tend to use 'early adopters' as guinea pigs.