James, I have not built, owned or flown a Rotax 912, but I have ridden behind some.,So I am not completely without expeience of this type.
I was a partner in a Starlite, which is a small homebuitl, about 250 lbs or so empty and powered by a Rotax 447. It is the single seat version that came from designer Marc Brown, before the Pulsar.It is too fast , well over 120 mph to qualify as an LSA, but fits otherwise.
I did the test flgihts, and while the Rotax performed ok, it sure did not inspire condience at first. It rattled and shook at low speed and began to smooth out above 3000 rpm. It never failed us.
I think the 4 stroke 912 is a big step up, but I would not necesarily say it is better than a good Continental O 200 etc. The samlll Lyc and Con have powered good planes for decaeds, and the O200 even pushes racers at Reno to 250 mph.If I am correct and not out of date the Rotax had a TBO of about 1200 hours vs. the 1800 or 2000 on the Lyc or Con.. Of course the Oh on the Rotax is much cheaper.
Both engines have their place as do both types of planes. But I haven't found any lite or LSA plane that I'd trade for my Cub.
To me, what is improtant is to get more folks out flying , not so much what they fly. As long as it is fun and safe.
I have very little experience in LSA,s , not that many around here; but I always try to beg borrow or buy a flight when I am at EAA.