Good hand sent morse should be just as good as machine generated morse, that is not an opinion its a fact, we were tested and trained using an inker to show just how long , or short the various elements were.
BUT, I do remember, all to vividly, one ship station that was so bad, we used to double up to receive messages from him on a bad day, and then the two of us would compare texts and endeavour to make the message out of them.
The one thing that we had to absolutely get 101% was the auto alarm signal sent by hand, 4 second dash 1 second space 12 of them in exactly 60 seconds, I would imagine if you had to send it by hand in the heat of the moment it would just become an automatic response.