On one hand, there have been multiple reports (mainly from groups with a long history of building T2S systems) stating that systems using source-side syntax greatly out-perform phrasebased systems (Mi et al., 2008;Zhang et al., 2011;Tamura et al., 2013).
there have been also been multiple reports noting the exact opposite result that sourceside syntax systems perform worse than Hiero, S2T, PBMT, or PBMT with pre-ordering (Ambati and Lavie, 2008;Xie et al., 2011;Kaljahi et al., 2012).