The AGUTEX style agupp puts the title, authors, and abstract on
a titlepage and starts the two-column mode with the first \section
command on the next page. Frankly, this looks cheap. By selecting the
option twocolumn explicitly, the title and authors are put on the
same page as the opening text, but the abstract goes into a narrow
column. (This is actually standard LATEX, so one should not complain.)
, on the other hand, puts the
title, author, and abstract all across the two columns of the starting
text.
This is illustrated on the first page of this paper.
Furthermore, the information in \lefthead and \righthead
are added in the running heads; the option twoside may be used
to effect here. This looks far more professional, more like a reprint
than a preprint.