What is the basic difference between XML::libXML and XML::DOM modules?

XML::DOM is a perl module. It uses/depends on XML::Parser/libexpat. Xpath support via third party XML::DOM::XPath

XML::LibXML is just an interface to gnomes libxml2 which is written C and supports DOM/xpath natively.

LibXML is faster and more memory efficient, but before strawberryperl wasn't as easily install-able on windows as XML::DOM

which one should I use?

XML::LibXML, and xpather.pl