A small MWE for testing SE BibTeX export with biblatex+biber vs bibtex+natbib

sebibtex.tex

\documentclass{article}

\def\testmode{old}
\def\testmode{new}

\usepackage{xifthen,url}
\newcommand{\ifnew}[2]{\ifthenelse{\equal{\testmode}{new}}{#1}{#2}}

\ifnew{%
  \usepackage[backend=biber]{biblatex}
  \addbibresource{setest.bib}
  
  % Print nameaddon if it exists
  \renewbibmacro{author}{%
    \printnames{author}%
    \iffieldundef{nameaddon}{}{%
      \ (\printfield{nameaddon})%
    }%
  }
}{%
  \usepackage{natbib}
}


\usepackage{filecontents}
\begin{filecontents}{setest.bib}
  @MISC{30073,
    TITLE = {Cutting equal sticks from different sticks},
    AUTHOR = {Erel Segal-Halevi (http://cs.stackexchange.com/users/1342/erel-segal-halevi)},
    HOWPUBLISHED = {Computer Science Stack Exchange},
    NOTE = {URL:http://cs.stackexchange.com/q/30073 (version: 2015-02-16)},
    EPRINT = {http://cs.stackexchange.com/q/30073},
    URL = {http://cs.stackexchange.com/q/30073}
  }

  @online{cs.SE:30073,
    title = {Cutting equal sticks from different sticks},
    author = {Erel Segal-Halevi},
    nameaddon = {\url{http://cs.stackexchange.com/users/1342}},
    howpublished = {Computer Science Stack Exchange},
    url = {http://cs.stackexchange.com/q/30073},
    urldate = {2014-11-26},
    date = {2014-09-17},
    year = {2014},
    month = {9}
  }
\end{filecontents}

\usepackage{hyperref}
\begin{document}
  Let's do a test. This is the old one~\cite{30073}, and this 
  the new one~\cite{cs.SE:30073}!

  \ifnew{%
    \printbibliography
  }{%
    \bibliographystyle{plainnat}
    \bibliography{setest}
  }
\end{document}