I think it is very clear there is a difference in detail in the picture i added to my former reply. For me as a professional photographer it is simply very important to get the job properly done. Therefoore i got me a multishot back and i use it very often and mostly in 4 shot mode and yes also color is much cleaner, especially when photographing dark textured things such as black or dark poweder coated metals for instance.
As there was no clear advantage in MS, i myself and a lot more people would not spent that amountof money on such a back.