I have both te MC and SC version and there is very little difference between them in "normal' shooting. Where they differ is at the 1.4 end. The MC exhibits a bit more contrast (as is to be expected). The SC has a softer look at f1.4 and 2, not "unsharp" just softer as to contrast.
If you are a color shooter the MC is most likely the way to go as you do get the apperance of higher saturation.
If you are primarily a bl/w shooter, the SC is the way to go. You get a bit more details in the shadows, less contrast type "blocking" up and a nice, smooth mid-tone range.
I dont think that the resolution is really different between them. The higher contrast of the MC gives it an appearance of sharpness.
Either one of these lenses are superb, particularly when you take into considering the cost!
I usually keep a M2 loaded and ready with a 40 on it (could be either a SC or MC) and it is the perfect package to grab when you go outside and want to shoot just for the fun of it.