KB was a pretty meaningless bauble that they might dish out to anybody they were feeling particularly well-disposed to at the moment.
KG was much more exclusive, as there were only 2 dozen slots. They had their own pews in the chapel at Windsor Castle and got to socialize with the king. It was almost like a non-hereditary earldom. Get a KG and you could think in terms of your son marrying an earl's daughter and your grandson being an earl. In fact a lot of KGs were earls already, but even for them it was a step up the social ladder.
