Okay my turn to voice which type of lawn I think is best
Personally, I like using a mixture of grasses, usually fine and red fescues, perennial ryes and blue grasses,that way if a fungal disease starts up which targets one particular type of grass there will be others present so the damage will not appear to be as sever. If you only have one type of grass a disease could wreck havoc on the lawn.
In drought situations the fescues will do better then the ryes or blues, in excess moisture, the ryes will fair better. Blue grasses do make a beautiful lawn, but tend to be a bit more troublesome and temper mental as far as extremes in temps, humidity and rainfall go.
John is right if it is a pure KBG lawn, since the
seed is so small,( 1/4 the size of the other
seeds) a little bit goes much further. Fescues are slower to spread, but I think the rye is pretty quick as well, but this would mostly depend on its care.