Do small breasts have a better survival rate with breast cancer because of early detection (via self-exam)? or are they handicapped by breast density?

Not a factor.: Breast size does not seem to change a woman's risk of getting breast cancer, her chances of the tumor being found early, or her chances of being cured. Small breast size may rarely limit some surgical options (lumpectomy/breast conservation) due to the final cosmetic outcome.

Possibly yes: Unless you have a lump do not worry. Breast size does not affect whether you develop breast cancer or not.