O.k.~We're going to confuse the daylights out of the original poster . . .
Here's the deal:
A Sporn, a Halti, a prong collar, etc.---They're all "devices" or "tools" that can be used to help train a dog to walk without pulling. None are magic. They all require work on the owners part as well.
A harness, a flat collar, etc.---Are simply choices of products that can be used to walk a dog . . . hopefully once they have been trained not to pull.
I, personally, prefer a tool such as a Sporn to help "train" my dog not to pull, along with voice command. Others prefer prong collars. I, personally, am not a prong collar person. It's all about preference and choice.
Once you get beyond preference and choice, you will find certain dogs respond well to some "devices" that other dogs do not.
I, as I have said, had fantastic luck using a Sporn as a device to help train my female not to pull. Now anyone can argue with me 'til the cows come home that I didn't "teach" her anything, that a Sporn is a tool/device for people who don't want to train their dog, that I shouldn't need a tool or device to train my dog, etc., etc. My response to that would be the proof is in the pudding---she can now be walked on a harness or a flat collar and she does not pull, when all else failed. I, personally, prefer a harness for all of the reasons I and others listed. You can not argue with success, whether you like my method of training or not, and it was all done in a positive fashion.
Some people will tell you they had no luck with a Sporn, but that they had great success with a prong. I don't like prongs . . . but be that as it may, I can't argue with a person who says they tried every other option to train their dog, and the only thing that worked was a prong, because it worked for them.
As long as no one is using methods which are considered cruel, I think it's awfully hard to argue with someone elses success.