I got a prong collar because someone posted some research to the shy-k9s mailing list back then. I can't remember the particulars very well, but it seems they autopsied a group of dogs that died of natural causes. Half had been trained with chokes and half with prongs. Most of the choke-trained dogs showed some neck or spine damage. Almost none of the prong-trained dogs did.
My dog has adapted somewhat to his missing rear leg, and I worry a lot about his neck and spine, since they curve a bit. So, I went out and bought a prong. Took it out of the sack thinking, "Eeeww, it really does look like it came right out of the Spanish Inquisition. Am I really going to put this thing on the big happy sap?"
A Lab-sized prong collar is plenty big enough to go around my own neck, so I sized it to fit me, and put it on, and very slowly pulled it tight. No pain. I gave a tug. Didn't hurt. I tried a jerk. No big deal. I yanked it as hard as I could several times fast. It's not painful. It's a strange sensation--little metal fingers closing around your neck from all sides--but that's it. Don't try it if you have a ticklish neck, but I can't see how it could cause a dog pain, even if s/he lunged hard while wearing it.
With Cass and with other rambunctious, outgoing, energetic dogs in my class, I saw the prong collar work very well. So, I'm not saying it's the right tool for all dogs, but if it does seem like something that will work for your dog, I don't think you have to be afraid of causing pain or being inhumane to your dog.
As a fashion accessory, it left a lot to be desired, and I haven't worn it since. And please don't forward this message to my boss. I'm a bit headstrong, and he might decide to invest in a prong collar for my working hours!