It becomes more obvious that the bi-bi approach is the better approach than any others so far it proved, if not perfect. We have to choose a system disregardless whatever they declare that all approaches didn't work out or aren't perfect, however. Sure enough, it is only my opinion that I think we ought to use the bi-bi approach yet they could always improve it along.
That's your opinion as far I've done my research, the disadvantage of bi-bi setting that it does not spend time working on audition or speech. You can find that information on here: Bi-Bi Options
I prefer if deaf children learn speech and signs, not one over another that's my opinion.