A few things, the width of collar can help prevent some damage but the pulling problem needs to be addressed. Slip/training (or choke as its sometimes called) or prong collars should only be used if you know how to use them properly (and there are "certified trainers who have no idea) otherwise you can cause your dog a lot of damage, physically and mentally. These collars are easy to misuse and one of the reason slip/training collars ended up being called choke chains is because of improper (and at time out right abusive) use. Martingales can come in both buckle or slip on style and can have either a "chain" or cloth loop, these collars are especially useful for dogs the like to or can slip out of regular collars. Some people feel that they are a more humane slip collar (although there are collars called limited slip that combine the martingale style with a slip collar) since the tightening can be used to signal the dog. I would use a wider collar if other options were not available and the pulling remains a problem.
I agree that loose leash training would be helpful. One way would be the "tree" method were you simply freeze and refuse to move every time the dog pulls, until they return to you. Some dogs are easy to train this way, others see it as a sign they need to pull harder. The way I've trained a few stubborn pups has been to use the "sudden turn". Basically, you start walking holding the leash at the length you want your dog to be at (for example heel position), when your dog starts to pull, call his name, once, and make a sharp (think military) turn away from the dog. You may end up going in a square for a bit. After a few times, calling his name and turning, stop giving him a warning and simply turn. Then start turning towards the dog, first with warning, then without. Either way, it takes a while, is fairly tedious and time consuming to train a dog to walk without pulling but worth the work.