Toying a bit with scratchboard to digital vs just straight digital this week.
This was done in Manga Studio and altered as a vector in Illustrator. I think the two main differences in the styles would be the digital has a tendency to make smooth concave dips that a knife would not make and there is less image debris (and also less detail). Digital may be a viable alternative to scratchboard for some illustrations (or large number of quick ones) but there is also the problem of not having a finished piece of physical art to sell afterwords which is sort of important from an income standpoint.
See full post here: Suborbital Decay2015-01-06.