Being "Notified", vs. being a true "secondary"

[Cormack, Ken]

Group,

We've just been asked to move the "primary" for 2 of our zones, to a new
server, and relegate our former primary to a secondary.  However, the
engineer responsible for setting up the new server has defined the old box
as a "notify", rather than defining it as a true "secondary", within the NS
re4cords of the zones being moved.

Personally, I'd rather see them as secondaries.  I have a feeling there are
important distinctions between the two configurations.  What are the
strengths and weaknesses of each configuration?

Thanks!

Ken