I guarantee if the Jabiru aircraft came with a Rotax option they would sell more, they have the runs on the board and have a lot of happy customers. I prefer the gearbox over direct drive any day, people will tell you that there are more things to go wrong with a gearbox but with direct drive, if there is any balance issues with the prop the crank will be effected more and the inertia will always transfer the load onto the one side of the crank that is hevier, with a gearbox the load will be spread out over all different points on the crank due to the gear ratio being different from 1to1.
From another direction, if you had 2 identical spec engines. same bore, same stroke, same bearing area but the only difference being 6 cylinder and the other 4 cylinder like an EJ22 and an EG33 from Subaru. the EG is just an EJ with 2 extra cylinders. The 6 would always last a lot longer due to the balence of the crank. In a 4 cylinder engine every 180 degrees the pistons are all totally stopped, this never happens with a 6 and as such the engine runs a lot smoother, this smothness adds to engine, gearbox and prop life.
If I was a manager for Rotax I would push for a 912 with 2 extra cylinders. oh yeah!!
Like the Maj said, "back the Aussie products when you can, but a spade is a spade"