Martingale collars help if dogs like to slip out of their collars. They’re just tightening flat collars, so again, you’re applying discomfort to the neck to discourage pulling. My dog wears a martingale, but he doesn’t pull. I like them for safety because if he were to back up or pull, the collar isn’t going to slip off.
The most effective collar depends on the dog. No dog is the same, and no dog responds to training the same. Some dogs are sensitive to body harnesses, while others use them as an extra boost to pull even harder. Some dogs will pull on a flat collar until their trachea collapses, while others make sure they walk lightly so there isn’t pressure applied.