I happen to love all boobies.. But set me straight... which are most sensitive. Big ones or little ones ?? I'm guessing little ones !!

I only know about mine, I can't speak for itty bitty or big ones. I have a B cup and they are incredibly sensitive.

I don't think size makes much difference. The nerves are in the nipples, the rest of the breasts is adipose(fat) tissue. Even many men will get erections if their nipples are stimulated. Most men resist this because they think it's too-"gay"- and indeed, nipple-play is a major part of gay sex.