I often experience problems sending and getting contact information in mobile devices due to some weird incompatibilities (they often arrive garbled, empty or don't arrive at all). So I use plain SMS text, which is uncomfortable on both sides. Therefore I have doubts on attaching vCards to emails - is it likely that the attached vCard will not be opened correctly? Is it safer inserting contact data to the email body?
I think it all depends on your interlocutors: