I think it's true that Rotaxes start better then Lycontinentals when cold, but they can be a pig when "warm" (shut down 30-60 minutes).
Losing the archaic mixture control (although it's an optional extra on a few installations) you do add the archaic choke control!
On most installations, you also lose the carb heat CONTROL, which is a big bonus.
The use of automotive fuels and oils definitely presents a huge saving (interestingly, I know a Rotax dealer who sells lots of 912 spark plugs to BMW motorcycle owners who use the same plugs, but they cost 4 times the price if sold for motorcycle use!).
On net, I also prefer the Rotax - and would point to the Tecnam P2006T as an example of a really good use of a 900 series engine.
G