If you want the smallest iPhone available, and prioritize that in your purchasing, you no longer have to compromise on a wide array of features to do so.
That will spur a great deal of people who are refusing to buy iPhones to buy iPhones (+$$$) and convert a certain percentage of bigphone users to smallphone users at a lower pricepoint at the next upgrade cycle (-$$).
It is possible that Apple's usage statistics for old iPhones indicate that the + will be greater than the - while getting a bunch of users off of older lower-performing phones.