Firstly, I'm not comfortable using any training collar other than a nylon martingale on a puppy under 6 months. Secondly, every collar is as good as the handler when it's used properly. If the handler isn't a good one and can't use the collar properly, then you aren't going to get good results. If the handler is an outright bad one and uses the collar WRONGLY, then you're going to get terrible results.
Prongs are one of the easiest training collars to misuse, and one of the most frequently misused.
Flat collars, chokes and martingales all put stress on the front of the dogs throat when the dog puts pressure on the lead. Prongs spread out the tension, thus are unlikely to cause trachea damage which is a main concern when selecting a collar for your dog.
The biggest downside I see in prongs is that they're so easy to misuse, and when they're misused even a little bit, the amount of damage done is astonishing.
Prongs are proven to be safer to dogs than chokes.
I've linked you to a webpage which includes brief information about a study done a few years ago, as well as more info on prongs.
"•100 dogs were in the study. 50 used choke and 50 used prong.
•The dogs were studied for their entire lives. As dogs died, autopsies were performed.
•Of the 50 which had chokes, 48 had injuries to the neck, trachea, or back. 2 of those were determined to be genetic. The other 46 were caused by trauma.
•Of the 50 which had prongs, 2 had injuries in the neck area, 1 was determined to be genetic. 1 was caused by trauma."
It's very interesting. Prongs look like torture devices, and it's so easy to make them into torture devices. Educate yourself before you buy a collar that can cause so much damage, so quickly, with so little effort on your aprt, and your dog will be fine; as well you.
For dogs that pull, I do prefer prongs, because the tension and pressure isn't applied to one area. It's spaced out around the neck. Prongs are uncomfortable, or if you'd prefer "painful" (you'd have to test it yourself, because you won't believe anybody else tellking you that it doesn't actually hurt), so the dog doesn't WANT to pull, which means you can train using a more positive method if you prefer - which you should.
I'll link you up to a bunch of other websites, with different views and approaches, so you can do research before jumping into anything. Every collar that's misused can cause damage. Prongs are one of the easiest to misuse.