Decades ago I had a friend who was an Environmental Health Officer and had done some stints in slaughterhouses.
He told me back then that, from his perspective, the main difference between Kosher and Halal was that for Kosher there has to be nothing adhere to the knife, so the knife has to be incredibly sharp, whereas there is no such stipulation for Halal. And back then, he said, some of the knives being used for Halal slaughter were very blunt, to the extent that there was a humane issue.
As I understand it, the regs have long since tightened this up, and knives for Halal slaughter now have to be just as sharp as those for Kosher.