A consultant hired by John recommended that, instead of reducing price, he consider a strategy that leverages a source of advantage valued by customers that is not easily seen, understood, or copied by competitors, such as subtle but important product innovations, improved product and/or service quality, innovative marketing programs, lowered costs of acquiring, using, and disposing of products, or new marketing channels with more efficient supply-chain customer benefits. What type of competitive strategy is the consultant recommending to John?