In my 28 years of being a dog owner (from toy to large breeds), I have tried just about every single type of collar available. Here is a simplified list of available collars which I hope helps you make an informed decision about selecting the right one for your dog.
Regular buckle collar: These generally serve no training/corrective purpose and are used for decoration and to display dog and owner identification information. They can be made in a wide variety of materials, most common being nylon and leather. You can maximize comfort and minimize irritation to your dog’s neck by feeling the inside of the collar for any sharp ridges or labels. (ie. plastic stitching that has been bluntly cut).
Standard Harness: Contrary to what the general population believes, this type of dog “collar” encourages pulling. Notice that this is the same collar-configuration that sled dogs use…they pull for a living! As a general rule of thumb, the closer to the dogs head, the more control you will have over the dog. Any harness where the leash clips at the dogs back will provide no control. Nonetheless, if you have mastered “the walk” with your large breed, or have a small non-pulling small breed, this type of dog collar might be perfect for you.
Head/muzzle collar: This type of collar works by applying a light amount of pressure at the muzzle and base of your dog’s neck, emulating a natural correction from a canine pack leader. One popular example of this type of collar is the Gentle Leader, you can find a Sniffing Snout review here. These types should be used for walking only- not be left on your dog permanently.
Prong/chain collars: These collars are extremely effective when used correctly. It’s a good idea to ask an expert how to find the right fit/size, figure out the correct way to place it on the dog, and the proper way to elicit a correction. Misuse of these types of collars could lead to desensitization and contradict the effects of training, or even worse, physical pain to your dog. Combined with behavior training, I found this type of collar most effective when trying to teach Mr.Brown how to walk “correctly.” This is still a work in progress 
You can find our prong collar review here. These types should be used for walking only- not be left on your dog permanently.
