My current H is a breast man and is very pleased with my figure. I am naturally busty. His first W was less than a handful, so obviously breast size preference was not the deciding factor for marriage. But the q concerns physical attraction. In our case, my H was initially sexually attracted to me for my eyes, hair and breast size.
H is very negative concerning breast implants.
That is a big turn-off to him although it may seem to be an improvement physically. This is an area where the inputs you get from men will be all over the map, I suspect. I've known two women with implants, they just felt it made them look more sexy and gave them more confidence. One was of above average intelligence, the other quite intelligent. But for me, the expense and risk would be wasted.