A regular collar goes not move. It stays at one adjustment.
Actually this statement is a fallacy when it comes to fixed buckle collars. I have seen MANY dogs choke themselves on a fixed collar when they lunge or pull. My first two dogs are a classic example of this. Before you ask, yes, my collars were adjusted to fit correctly. They are supposed to be adjusted so you can slip 2 fingers between the collar and the neck.
My Malamute had an issue with an elongated esophagus and was constantly choking herself on a standard buckle collar to the point where she'd take 5 steps and have to stop to cough very hard.
At the park I see MANY MANY MANY dogs on standard buckle collars that manage to choke themselves on it as they walk (pull) their owners along or lunge at other dogs.
I switched to a Martingale with my Finnish Spitz, Melody, when she was an older dog because she was starting to really choke herself when walking on a flat buckle collar. She did not choke herself again after that switch.
Because the Martingale fits loose, it slides up and down the dog's neck. When properly adjusted, it is only as tight as a standard buckle collar around ANY point on the dog's head/neck. With a Sheltie, who's head is narrower than their neck, when they panic and try to bolt, the martingale collar moves easily up the dogs neck often stopping right behind or just below the dog's ears - the point where a Sheltie would escape a standard flat collar - still at the equivalent tightness of a standard buckle collar when adjusted properly.
I've put my martingale around my wrist and pulled as hard as I could. There was NO PINCH whatsoever. (For the record, I'm rather overweight and have big wrists, not little twigs.) I check my setting regularly to make sure its not too tight or too loose fitting; something you should do with ANY collar due to blowing coat, weight loss/gain, etc.
Martingales ARE NOT meant to be used as corrective collars; they aren't designed to be corrective collars. I won't say they can't be since anything can be abused. Heck, if you are concerned about choking dogs, what about the people who use FLAT COLLARS as corrective collars and yank on them so hard the dog does a 360 degree turn on its back legs!? I've seen that!
Honestly, after using both a flat collar and a martingale collar on my dogs, I have to say I had fewer choking incidents on the martingale than a flat collar. Your mileage may vary and this is
strictly based based on my personal experiences with both collars in question.