With my hands, if I were strong enough, I could hold two ends of a chicken's neck and pull. The vertebrae would part, the cord would snap, and the chicken would die through having its neck broken.
I do not see how using a piece of metal to push two vertebrae apart is different. Apart from it's surer.
There is no difference, I agree with you, a dead bird is a dead bird and whatever method you use if you end up with a dead bird you have succeeded, whether that's neck dislocation, shooting, bleeding, electrifying, decapitation etc etc they will all kill.
I'd argue the wall despatcher is surer, as Stereo says its all to do with the operator, someone competent at manual neck dislocation will kill a bird every time and exactly the same with the despatcher.
However we are talking about humane killing and at the moment wall mounted despatchers are considered an inhumane method of culling poultry, however efficient they may be.
You could argue cutting their heads off with a pair of garden shears or an axe is a 100% efficient way of killing poultry but its not a humane way
Stereo, the stunner is a stunner only, however I would seriously doubt any animal would ever recover from the blow, it will still need to be decapitated, bled or have its neck dislocated after stunning.
When I stun the pigs with mine there is no way they'd ever recover from the blow.
I bleed them after stunning but if I didn't they wouldn't regain conciousness.
Of course we also have Kosha and Halal killing here in the UK