What is the house edge in blackjack if the dealer "stands on your score"?

what is the house edge in blackjack if the dealer only hits on anything less then what you have, stands on the same number, and wins If he beats you? example, say the player has a 20, and the dealer has a 17....and will always attempt to beat you by hitting if he has less then you do. and vice versa, if the player stands say a 13, and the dealer flips and is allowed to stand a 14? also would it be better for the dealer to stand on your score and pushthe hand if he has a soft of the same number? or hit it?