Many are mentally goofy....they are so self conscious it is rediculous.
Smaller breasred women are more mentally advanced and mature as well as healthy.
On the other hand, larger breasted women may tend to be less psychotic.
Just my opinions though.
I doubt they have a stronger drive because they are usually less healthy. Many are cough potatoes. Lie on a couch and eat potato chips.....your tits will grow.