Hi Yael,
Just quickly, the differences between BM and formula is that BM is metabolised & digested so much quicker by the baby than formula is. BM will always meet your babies energy requirements perfectly... however I believe it is more possible to overfeed a baby on formula.
Although as a side note, I too have heard that even babies on formula will stop stucking or throw up if they've had too much....
But I think as a general rule, FF babies put on weight quicker then BF babies, which I guess could be another reason?

And due to the composition of formula, it takes a lot longer and more work for the babies to digest it as its heavier and more filling in their bellies, - thats why they usually recommend a 4-hrly gap between formula feeds.
Whereas a baby can have BM as much as often as it needs, which is also really good for keeping up the mothers milk supply.