This debate would be perfectly valid if it was considered abhorrent and wrong to kill animals for meat but it isn't. Whichever way you kill an animal, it is not going to be nice. Even when an animal is stunned, it is distressing for an animal. The animal doesn't say "don't worry about me. just stick your knife right there. I don't mind because I've been stunned."
It is still a perfectly valid debate because there are degrees of cruelty. If an animal can be stunned before slaughter so it doesn't feel any pain, then there's no reason I can see why that shouldn't be done. Yes, it will still be distressing for the animal, but less so than being slaughtered without being stunned.
If there was a higher species who fed on humans, I doubt they would give a shit about our suffering.
Then they wouldn't deserve to be called a higher species.
The issue I have with this debate, however, is that it started off in history as a racist debate and although there are people in this debate who care about animal welfare, that racist element still exists and it is not a small element.
That issue is based on a logical fallacy. Mussolini famously made the trains run on time, Hitler reduced the unemployment rate in Germany. Should we now be suspicious of anyone who wants to improve the rail service or create employment, because they share some policies with fascists and Nazis?
In Korea, dogs are killed by being beaten to death and live octopus is a delicacy (where a living octopus is brought to table and has its tentacles chopped off at the table!). In Florida, crabs claws are a delicacy, and they don't even kill the crabs! The claws are chopped off and the crabs chucked back into the water.
In the grand scheme of things, halal and kosher is not really that bad.
There are far worse and more widespread abuses, I pointed that out in my first post in this thread. However, that shouldn't stop halal and kosher slaughterhouses from updating their practises when technology arrives which can lessen the suffering for the animal.
Islam apparently doesn't even have a problem with stunning the animal before slaughter! So what is the problem exactly? Most Jews are secular anyway, so in effect animals are being put through unnecessary suffering to appease the sensibilities of a handful of ultra Orthodox Jews who should just be reminded what century they are living in.