An old fogey mechanic once told me that SS props would cause your motor to fail eventually. He didn't know much about boats I guess.
A minor event with the bottom of the river may cause a slight ding in a SS prop, where the same event would require a rebuild of an aluminum prop. The damage in the pics above would destroy a lower unit, no matter what prop was on it.
SS is simply the way to go, if only from a performance and fuel economy standpoint.