DOM Manipulation in Wordpress (and elsewhere) using php

I'm quite new to the DOM manipulation world and I would like to get a head start in order to avoid common errors.

I am looking for the most efficient way to manipulate content generated by wordpress using php. At the moment I am using Simple HTML Dom which seems to work just fine. However I recently found DOMDocument and a few others and it would be very helpfull if someone cleared out which one is faster, better or at least will generate less errors in case of really bad markup.

Also on the side can someone explain what is this syntax (instead of $html this @$html)

Thank you very much