If I were looking for a doctor or a lawyer (or other such professional) and I see two listings- one for Maddy Jones and one for
Madeline (even Madalynn for that matter) Jones, I'd opt for
Madeline. Why? It just sounds more professional. Maddy would give me the impression of a younger, less experienced person who hadn't yet learned that her full name (as I would assume she had one) comes off as more grown up.
Sure it's all speculation and assumption just looking at the names, but our names written out for all the world to see sometimes gives the first impression of us. A full name, imo, gives a better impression in certain situations. Having a full name gives options for all stages of life.
While I agree that you should use whatever name you like best, I would be aware that while you like a nn, it may not allow your child to put his or her best foot forward in every situation. Not all nns are created equal though, some sound more formal than others,
Lily and
Jack, for instance can stand on their own without sounding like a nn.
That's just my take on nns versus full names, based on my experience in which most everyone I've come in contact with who has had a nicknamey name has also had a full name backing it up.