People often ask if head halters are better to use instead of a collar or harness. The question needs to be clarified “better for whom”? For dogs no, as explained below. For the human they provide you with better control of a dog that is out of control, but I only recommend their use in very rare cases for the reasons explained below.
How much does your dogs cooperation weigh? by Suzanne Clothier
There are numerous types of head halters that are recommended by trainers, pet store employees, your friend, neighbor, etc... (Sadly) The reason people resort to a head halter “tool” is because people cannot control their dog. e.g. pulls on leash, reactivity, etc… Does a head halter deter a dog from pulling while on a leash? Yes. Understand that a head halter device is a restraint device and management tool. For me a head halter “tool” is a tool of last resort. It should never be a “go-to” device to control a dog unless it is an exceptional situation. (And there are far to many used currently) As with all tools there are very limited times for their use. Sadly they are over-used in the name of being humane, positive, kind, etc…
Our approach to training needs to take into consideration the reason for the behavior or reactivity. If the problem is limited to a dog pulling on leash, simply teach them to walk without pulling! (See Video) Reactive behavior can be motivated out of fear, excitement, frustration, or aggression. Far too often I see people using aversives on a fearful dog. This can shut down the overt display of reactivity but does not help the dog or the problem. Not to mention this is very unfair to the dog
There will be some who compare it to a halter a horse wears. Its important to understand dogs are vastly different from horses with regards to structure and anatomy. On a horse a halter sits well down the long bony part of muzzle away from eyes. With dog’s it often sits just under the inside corners of the eyes where the skin is sensitive and thin. When used on a horse the pull is sideways and down. On a dog the force is up and to the side which is completely different and has potential for harm. Dogs are not prepared for this jerk or pull trauma. 
When using a gentle leader or any type of head halter “tool” please don’t intentionally place your dog in a situation where they are known to react or likely to react. There is no real magic to a head halter. This is a restraining device that should only be used for a very short time when appropriate (with caution), and they are not appropriate for all dogs. (nor recommended) How we work with a dog with behavior/training problems is totally dependent on what is motivating the behavior. Reactive dogs need the least distracting environments when we start to work with them.
There are basically two types of head halters. One type the point of control is under the chin and works by pulling the dog’s head back to the side. The other version has the point of control at the back of the neck and when pulled places pressure on the dogs face. We should always take into consideration the dog's anatomy when we use any type of equipment. Head halter devices/tools have their own set of concerns; potentially harming the Trigeminal nerve, facial nerves, soft tissue and spine damage. The head halter devices that tighten behind the head have added issues so we must add to the list potential damage to the nuchal ligament, and the spinal cord from skull to the upper cervical vertebrae. The Problem With Head Halters https://suzanneclothier.com/article/problem-head-halters/
My view is that that all equipment is used to either train and/or restrain the dog and can be viewed as aversive. People often ask what “what equipment you would use for a reactive dog?” I recommend a properly fitted martingale for every dog in training. That being said with large dogs that are completely out of control, on rare occasions I do use a “One piece halter and leash combo” from genuinedoggear.com along with the martingale collar. I like this product because it is very soft tube webbing that lays flat. I place the one piece halter leash loosely on the dog and fasten the one piece leash to my regular leash and only add pressure when necessary once I have moved the dog next to me with the martingale. I use it like an emergency brake when the dog is close so as not to create spine problems. My goal in dog reactive cases is to teach the dog to ignore other dogs. For me it starts with the dog overlearning how to walk properly on a leash. (Loose leash walking) I have posted a video of the technique that I use here. https://youtu.be/sF0udU6cz_g Choosing A Dog Collar
When using any equipment (including various leads/leashes) or training techniques I think we should look to the dog to see if it is having a suppressive effect in a negative manner. If the dog starts as happy and eager what is the effect when equipment is added? Is the dog still engaged and happy? By just adding equipment is the dog acting as if they are experiencing non-contingent punishment and no longer engaged with us? If we take the equipment off does the dog visibly brighten? Does the equipment/training provide the dog cues to exercise self-control or is the very nature of the tools/training to provide a sedating/inhibiting effect because the dog is working to avoid punishment?
Another important point to make is that I don’t let the dog move forward unless they are exercising self-control. Meaning they will not exit the house, gate, or car unless completely under control and I have given them permission. I’m very careful not to move so fast that I’m rewarding them for persistence. For example, as soon as they exit I will often request they sit while I calmly shut and lock the door. If the dog is not a wild child I really don’t care if they sit as long as they wait patiently for me. If this means it takes 10-minutes for them to exercise self-control I take the time because soon the dog will realize that his persistence gains nothing. Consistency will result in a dog cooperating in a shorter amount of time as you continue to practice. Thresholds, Thresholds, and Doing Nothing https://youtu.be/VLriCeTYxLM
I’m big on “permission” when working with dogs. Meaning I want them to sniff and have opportunities to explore. But it must be with permission. Many owners get this wrong. The dog will be distracted and pulling and just as soon as the owner pulls/guides the dog back to where it should be they give the dog “permission” to move away, sniff, explore, etc… What they get wrong is there was not a 10-second disassociation time between guiding them back and then releasing them to sniff. The dog was likely rewarded for persistent, not being under control or cooperating.
It is also important to evaluate whether the dog is getting all their needs met (attention, social interaction, exercise, mental stimulation) and making their life more interesting. Variety can be the key to an enriching life for dogs. Engage all five of the dogs' senses, to make their days more interesting. Anything that is unchanging is no longer unique and loses its value quickly. Dogs engaged in enrichment activities are less likely to develop the inappropriate behaviors that are the result of boredom, stress, and frustration. https://www.homeskooling4dogs.com/enriching-your-dogs-life
Many times people use these “tools” because they have heard/believe that a collar can cause damage to dogs. Yes a collar can cause damage to dogs. Dogs can and do suffer from cervical and back problems but I believe they are most likely caused by old school type (jerk) correction training. It’s my opinion that the causes of trachea issues that are not genetic are untrained dogs with heavy pulling, harsh corrections, especially with thin, metal, or any type of choke collars. To avoid inflicting damage do not use choke chains and other thin collars and do not place any collar high, right behind the ears.
I work with Chihuahuas to Irish Wolfhounds, and everything in between. In my opinion the equipment or tool with the least amount of risk when fitted (Just tight enough so the dog cannot escape the collar at its tightest) and used properly is the martingale collar. I prefer to use a wide and soft martingale collar 99.5% of the time when I’m working with dogs. But it’s important to me that dogs are under control and cooperating and I also teach dogs and owners how to walk on a leash nicely.
Whatever tools you use, look to make it as pleasant as possible for the dog while still maintaining control. We ultimately want dogs to desire to be with us and not find us punishing.
Understanding all that, a head halter does give the most control but if we choice to use it should be for a very short period of time and with the utmost care.
Before Placing any equipment please take the time to read the short articles below
Selecting Training Equipment https://suzanneclothier.com/article/selecting-training-equipment/
How Much Does Your Dog’s Cooperation Weigh? https://suzanneclothier.com/article/much-dogs-cooperation-weigh/
Handling On-lead Aggression https://suzanneclothier.com/article/handling-lead-aggression/
Guidelines for Teaching Self Control https://suzanneclothier.com/article/guidelines-teaching-self-control/
Understanding Thresholds: It’s More than Under- or Over- https://suzanneclothier.com/article/understanding-thresholds-its-more-than-under-or-over/
Training or Restraining? https://suzanneclothier.com/article/training-or-restraining/