The Cardini change (and it's variation) can be performed absolutely silently, due to the break, whereas there has to be at least a small amount of noise with the Ego change because there will always be friction between the top two cards.
uh. nope.
the ego change can be performed silently. it depends on the amount of pressure and how you pivot it off the deck. at MOST it'll make the same amount of noise that a cardini change makes.