Recently, (Junczys-Dowmunt et al., 2016) performed a very extensive experiment in which the performance of NMT is compared with PBMT and hierarchical SMT on multiple language directions and showed that NMT systems in almost all the cases outperform their SMT counterparts and to solve the only remaining issue which is the decoding time of the NMT systems, they introduce an efficient neural decoder which makes it feasible to deploy NMT systems in-production line.
all their experiments are performed on one single domain for which there exists a very large training corpus.