I would choose the framework according to your goals - OpenNMT-py is very research-oriented and hackable. It supports Transformer, copy-attention, image/speech/

I would choose the framework according to your goals - OpenNMT-py is very research-oriented and hackable. It supports Transformer, copy-attention, image/speech/text2text and more. If you are more production-focused, maybe MarianNMT or OpenNMT-tf are for you.