Note that, since the Berkeley parser is based on PCFGLA grammar, it may fail to get the syntactic outputs for some sentences, while the other parser does not have that problem.
early work showed that syntactic information is crucial for learning longrange dependencies, syntactic constituency structure and global constraints (Punyakanok et al., 2008;Täckström et al., 2015), while initial studies on neural methods achieved state-of-the-art results with little to no syntactic input (Zhou and Xu, 2015;Wang et al., 2015;Marcheggiani et al., 2017;He et al., 2017).