You do understand that with updated 5S Apple may make it that way, you are describing it, and every year they may show 3 sizes of iPhones with the same, or similar specs but different screen sizes and price points?Oh my. No please. Three screen sizes, sure, but please keep the performance the same. Just because I want a 4" phone, doesn't mean I don't want top shelf components.
Sure, make the argument that the extra space in the + model allows for more power. I am saying l, hoping, Apple leaves it out. Make the decision easy by limiting the difference to one core feature: display size.