The best performing systems being for character unit the RNN-transducer with additional attention module, achieving 7.8% in terms of CER and 17.6% on WER. For subword units, classic RNN-transducer, RNN-transducer with attention and joint CTC-attention show comparable performance on subword error rate and WER, with the first one being slightly better on WER ($17.4\%$) and the last one having a lower error rate on subword ($14.5\%$). 
 Question: Which model have the smallest Character Error Rate and which have the smallest Word Error Rate?
character unit the RNN-transducer with additional attention module For subword units, classic RNN-transducer, RNN-transducer with attention and joint CTC-attention show comparable performance