Thanks for the responses, but I think my initial query must have been unclear.
I am asking for the optimal strategy for the dealer. That is, if a casino were to redesign the rules, what would benefit the house the most. Assume the dealer still plays by a rigid set of rules that is independent of the players' hands.
I.e., would dealer hits to hard 16 and soft 18 benefit or hurt the house?
what about dealer hits to hard 15 and soft 17? how would that change the house edge?