I use a halti for GiGi the 2yr APBT I just adopted. I feel like they are like all training aids and should be used carefully and correctly. I don't believe that all dogs benefit from them but some do. The main thing I don't like is that they closely resemble muzzles which promotes the pitbull aggression stereotype.
GiGi is high energy, high prey drive, dog aggressive (out of insecurities) , and very wary of strangers. Neck collars and harnesses don't work because she just drops down low and pulls right through them. The head collar was necessary #1 for control so she doesn't get herself in a bad position with people/other animals. #2 it refocuses her attention and puts her in a state of mind to hear direction. There is no reason to use it in a harsh way and as her confidence and calm continues to increase and her relationship with me as her handler increases then the halti will no longer be needed. For her it is not a overbearing or enslaving tool, but rather a way to better communication when she gets in that tense agitated frame of mind.
I adopted my Boxer as a 4yr old and he pulled like crazy the head-collar was not a good option for him and neither was a neck collar as he has very sensitive skin and both put strain on his spine. I used a Holt harness with him and it was the tool he needed to get his focus without harming him. The halti was not a good option for him as it was uncomfortable and hurtful to his pride so he fought like crazy or dragged along depressed. He still has more to learn/work on (don't we all) but he walks like a gentleman on or off leash.
I am not a dog trainer but have learned a lot in general by training horses. My conclusion is treat all training aids and tools like what they are, aids for better communication, also with care and respect. No Training method works for every individual animal and you need to hear it when they tell what works for them. I feel like it all comes down to relationship and communication. Training should be a positive bonding thing
at least thats my opinion