I would say this depends on your bibliographic style and personal taste.
Using biblatex and the default style, you can get (code below):

On the other hand, if I use @unpublished rather than @phdthesis, the
output does not show anything about this work being a phd thesis. any
ideas?
There is something else : the school is not printed, so you have to tweak to add it (as a note, or something else).
Personally, I would definitely choose the @phdthesis for
- This is what this document is,
- It will be easier to update your
bib file, as you will just have to comment the unpublished.
- It reflects the fact that this document is "scholar".
Code :
\documentclass{article}
\usepackage[backend=bibtex]{biblatex}
\RequirePackage{filecontents}
\begin{filecontents*}{bib.bib}
@phdthesis{mephd2014,
author={Myself, Roberto},
title={A great memoir},
school={UCXDX},
year={2014},
note={unpublished thesis}
}
@phdthesis{mepdh2014bis,
author={Myself, Roberto},
title={A great memoir},
school={UCXDX},
year={2014},
addendum={unpublished thesis}
}
@unpublished{meunpub2014,
author={Myself, Roberto},
title={A great memoir},
school={UCXDX},
year={2014},
note={unpublished thesis}
}
@unpublished{meunpub2014bis,
author={Myself, Roberto},
title={A great memoir},
school={UCXDX},
year={2014},
addendum={unpublished thesis}
}
\end{filecontents*}
\addbibresource{bib.bib}
\begin{document}
\noindent
\verb|@phdthesis| with note: \cite{mephd2014}\\
\verb|@phdthesis| with addendum: \cite{mepdh2014bis}\\
\verb|@unpublished| with note: \cite{meunpub2014}\\
\verb|@unpublished| with addendum: \cite{meunpub2014bis}
\printbibliography
\end{document}
%? – Sverre May 27 '14 at 18:43@miscentry type, you could put the "unpublished thesis" bit -- or should that maybe be "to be published thesis" or "Ph.D. thesis, fortcoming" -- in thenotefield. – Mico May 27 '14 at 18:59yearfield.year="2014, to be published", or similar. – cslstr May 27 '14 at 19:45