Breast shape > nipple shape > size > jiggle.

Shape is more important.
I’m not attracted to a woman that has the body of a regular rock,
lamppost or dishwasher or I’d be physically attracted to those things.

The right size is only a small bonus and the bigger they are, the more attention it brings.
Jiggle also brings more attention to them, but size is more important as it (falsely?) implies easier arousal.

They’re also soft, thus very kissable and there’s nipples on them that can indicate and entice arousal.