I have noticed many try to decide which collar would be the best for their dog. There are many options out there from a plain buckle collar to an electronic collar. It can be most confusing so I thought I would share some collar information with you.
It is good for your puppy to learn to wear a collar immediately. This is the first step totolerating to walking on lead. This is also a way for your dog to be easily identified if he can wear an identification tag. Do remember that the collar should be properly sized for safety. If you leave a collar on your dog at all times may I suggest a "breakaway" collar. Some can and do manages to catch themselves. If you are gone for long hours at a time or unable to safely supervise them this is a very good option.
Buckle collars made of made of nylon or leather are nice collars to begin walking your pup with. This offers just enough protection so your pup cant get away if properly fitted.
There are many different training collars available. Remember these collars are only as safe as the hands that are handling them. They should NEVER EVER be left on a dog unless he is walking on lead. Many can be quite dangerous on an unattended dog.

Chain collars - this has a slip effect so the collar can tighten and not slip over the dogs head. This is also used by many obedience trainers as a means for making "pop" corrections to a dog. These should not be used on young pups.

Martingale or Lupine collars - These colllars also have a slip effect but will not tighten beyond a specific point. These are great collars for a more gentle correction approach. These are also great for overweight corgis that can often slip a buckle collar.

Prong collars - I would rarely see the need to use this on corgis. This collar does put pressure at the points around the neck. In my obedience classes I generally recommend them for the larger "bullish" type dogs that were difficult to get their attention. Never would I consider them for a fearful or aggressive type dog. These should never be yanked on, used with a flexi lead or without proper instruction to use them. I have seen many dogs loose at a park wearing one of these or a chain collar. Recipe for disaster!

Gentle Leaders - I have found these useful for some dogs that are heavily distracted. Once again I would not use this on a young pup as they do need time to adjust to walking on lead and learning about the enviornment around them. These can be a great tool in the right hands as like with the prong collar they offer a self correction when a dog is pulling.

I would rarely see a use for an electronic collar unless someone was doing distance work in advanced training. Electronic collars can do far more harm then good unless being used by a kind and experienced trainer.

Harnesses - generally not a favorite of mine. I find that many dogs that use them are encouraged to pull more. One only need to look at how sled dogs are outfitted to pull. If you personally like them and your dog is a good walker already on lead they are fine.

Proper sized collars are also most important. When measuring for a chain collar measure around the largest part of the head and add two inches. When measuring for a regular buckle collar or martingale collar measure the neck and purchase a collar in the size range. Remember pups grow quickly so check the fit frequently. For prong collars and gentle leaders it is best to have an experienced person help you. Both are dangerous and pretty much useless for correction unless fitted properly. For harnesses they must be tried on. There are so many different designs available that trying on is the best way.

Hope you find this helpful in making good choices while purchasing collars.