A typical, textbook example of the AU58 grade should really be aesthetically more pleasing than the similar MS60-MS61 coin. The reason for this is that a true AU58 will have few surface impairments, but will have only the slightest trace of rub on the highpoints whereas the true MS60-MS61 will have numerous surface impairments, but have absolutely no rub. Therefore, if one were to take a true MS60-MS61 coin and introduce the slightest trace of rub on the highpoints then one has a coin that is inferior to the textbook definition of an AU58 and would have a coin more likely in line with an AU55.
If one is doing a full Morgan set, they better darn well LOVE AU coins, especially the 1884s. Otherwise, they will end up broke, divorced, or both.
