I was curious, so I tried that performance test you linked to on my machine with the various parsers:

    ==== Total trials: 100000 =====
    bs4 lxml total time: 110.9
    bs4 html.parser total time: 87.6
    bs4 lxml-xml total time: 0.5
    bs4 xml total time: 0.5
    bs4 html5lib total time: 103.6
    pq total time: 8.7
    lxml (cssselect) total time: 8.8
    lxml (xpath) total time: 5.6
    regex total time: 13.8 (doesn't find all p)

bs4 is damn fast with the lxml-xml or xml parsers