In my situation it is just very useful to throw the .nzb onto
something which (typically) runs on a remote screen session on some
machine accessed over ssh (low bandwidth between office and
"download machine"). Thus I can even avoid the traffic which the
progress meters of nzbperl are generating by simply detaching from
screen.
Another advantage of nzbperl is that it just needs a text console
and very little resources (a few perl modules). Pan needs the
whole gtk stuff which is not strictly necessary for the download
process itself.