The O-233 is still heavier than the Rotax, but simpler. If the weight works, great - the O-233 is simpler and probably easier to maintain - no gearbox, no dual carbs. However, weight is going to be a problem with the O-233. The 912S works so well on the 1,320 MGTW LSAs because of its light weight.
If you could get a LSA with the O-233 to a useful load of 550lb , I'd say that was great. 500lb ... Ok. 450lb? No - that's not even 2 "standard" adults + 20 gal of fuel.
We have 605lb useful load in the CT with the 912S. I'd give up 40 lb to have the simplicity and "A&P friendly" nature of the O-233. On a heavier airframe like the RANS S-19 (about 800lb empty) the additional weight of the O-233 gets to be significant.
TODR