[oergiR]

I know that Andrew Ng and colleagues say that they don't use HMMs. I haven't spoken with them (I haven't seen them at speech conferences) so I do not know whether they actually believe this themselves.

I believe the best comparison between "CTC" (which is billed as recurrent neural networks without the HMMs) and the traditional approach is by people at Google, Sak et al, "Learning Acoustic frame labeling for speech recognition with recurrent neural networks", ICASSP 2015. (I can't find a PDF online.)