It's basically down to the different types of carbs used.
Some other points to add:
The Rotax 912 is available in certified and non-certified variants - the same parts are used. There are a number of certified aircraft using 912 engines (including the IFR Tecnam P2006T twin).
As for wear life (or if you like, reliability), the 912S (or ULS) has a 2000hr/15 year TBO. The average Lycoming also has a 2000hr but 12 years by calendar life.
The cylinder heads in Rotax 91x series engines are liquid cooled so the CHT sensor is effectively measuring coolant temperature.