I have the C3 and I've been a bit disappointed to be honest. Visor slams shut over 55mph and it fogs a fair bit, even with pinlock, compared to my old Shoei. I used my old shoei a few weeks ago again, and the C3 is definitely quieter, but then I'd normally have earplugs anyway.
But I think my biggest issue is that it's incredibly uncomfortable when wearing glasses after a couple of hours.