The advantage that XML::Parser has over XML::LibXML is that the former bundles the C-level parser with it (James Clark's expat parser). While XML::LibXML is in fact faster (and supports a real SAX interface layer), it requires the presence of libxml2, which is generally a part of any GNOME-enabled Linux environment, but may not be present on other systems. They can retrieve and install it, of course, but that is an extra step that may deter some people.

If you have enough control over the environment in your situation to ensure that libxml2 is not a problem, then I would recommend going with XML::LibXML.

--rjray