in borderline you create persona's knowingly and you "become" like someone or something you want to be in different situations or environments. With DID it's not a form of creation and the personalities usually are not consciously there for the host. They are not integrated at all with the host personality. With borderline it's a full manifestation of a conscious personality though it is never stable.

They do not relate much at all. I read this huge article about the difference but I can't find it. When I do or even can find it I will post it for you.