[watwut]

The other difference is that while chocolate bar makes you more active if you was low on sugar, you are still quite empty, hungry and looking for more to eat shortly after you ate that.

If you eat apples, you hit limit soon. Apples also do not work all that much if you actually need quick energy when doing something straining. It does not have that "immediately feel better" effect (which motivates you eat more and more).