Ear. Drops them like a rock. You most certainly don't want to be much forward of the ear, because if you get a little low, it seems to me that you could end up with a jaw shot and a wounded deer. If you're back by the ear, and you go a little low, you'll get spine, and/or jugular and they're still going to be dead instantly. Be aware that they do tend to twitch a bit afterward, kinda like when you chop the head off a chicken.