Mumi - I've read some evidence about how halal is more humane.
I no longer have the article, and can't find it online (must be on there somewhere!)
It basically said that halal killing severs something in the neck, which means that due to the speed of the cut, and the sharpness of the knife, the animal does not feel anything.
There were brain scans done on animals killed in the standard way, and the halal. The brains of the animals killed using the standard slaughter method still registered massive amounts of pain (although the animal was unconcious by then) The halal method, the brains barely registered any pain at all.
As far as I remember, the RSPCA did some research using their own employed slaughtermen (but again, I can't find any info online, so take this with a pinch of salt!) comparing standard and halal methods, that showed lingering deaths in the halal slaughtered animals, but it was later claimed, by genuine halal slaughtermen, that the knives used weren't sharp enough, and the cut wasn't deep enough to ensure nerves (or whatever in the neck) were severed immediately, so the research was invalid.
I have no problems eating meat no matter how it's slaughtered, as long as the animals in question have lived free-range lives.
When a chicken spends its life in shit conditions, I think killing, no matter how it's done, will be a mercy to the poor things!