girlfriends are bad , wives are worse 
(ROOT (S (S (NP (NNS girlfriends)) (VP (VBP are) (ADJP (JJ bad)))) (, ,) (S (NP (NNS wives)) (VP (VBP are) (ADJP (JJR worse))))))
(ROOT (S (S (NP (NNS )) (VP (VBP ) (ADJP (JJ )))) (, ) (S (NP (NNS )) (VP (VBP ) (ADJP (JJR ))))))