They are both efficient and humane.
Though the process done manually is more humane and less efficient.
I got no problem with either and if the consumer understood what happens to meat that is harvested in an inhumane manner they would agree.
In fact, I think it would be an object lesson to place to identical pieces of meat, processed, prepared and cooked in identical manners.
They will understand what the animal goes through when they bite the meat that was not harvested properly. Sucks, both in flavor, texture and one’s rightness for respecting life.
Now with these "humane" groups you'd practically have to hold and pet and calm the animal before killing it. You really have to think of the expression "humanely kill" ....