What's the difference?

I've been asked several times, what makes feeding a 'little' dog different than feeding a big one.  Well for one thing Zoey my 4# chihuahua only eats 2oz per day whereas Shellie my golden retriever eats 20x that much at 22oz per day.  Little dogs I have found don't need bone in their meals as much once they are off of the introductory period.  Zoey only gets bone 2x a week, Georgie gets bone every 3-4 meals, Shellie (who has a sensitive stomach) has to have bone every other meal to regulate her stools.  Another difference, is feeding 50% red meat (which I've heard is the ideal) isn't that difficult to do since a 2# roast will make 32 meals for my little Zoey and I got one for $3 so that made each meal less than 10 cents, you can't argue with that.  As far as organs go, Shellie gets them daily, my little dogs get them once a week.  Those are the main difference I am finding, as well as what 'boney' meals they can handle.  Zoey won't attempt to eat anything other than a pork neck bone, a cornish hen bone or the meat off of a beef rib bone.  She doesn't like the bigger cuts of meat either.