From what I can tell it's better to donate to a public bank. According to the AAP the child itself is almost certainly not going to be able to benefit from their own stem cells because whatever disease you're trying to treat them for is most likely already present in the stem cells. It can be used to treat siblings though. But overall the advice is to donate to a public bank unless you already have a child with a medical condition in your family that could benefit from cord blood from their sibling.

http://pediatrics.aappublications.org/content/pediatrics/119...