Both have a purpose. Some people like a collar and a harness, and vice versa. I like both.
Let’s first talk collars. A collar is easy to put on and leave on. But there is more than one kind.
The most common is the flat buckle collar. Then there is the martingale style, which is sometimes called a combo collar or limited-choker. There is a purpose for both types. (I use a martingale/combo collar on my Freya.)
With any collar, it is easy to attach a leash to it (usually). You can even hang identification and rabies vaccination tags from it. All good in theory.
Next, there are harnesses. They do look great. A number of companies have created all sorts of styles from a wide variety of materials. You can even buy some with rhinestones. But, whatever you choose, be smart about it.
Harnesses do not choke the dog if it pulls - if it’s the right one and is fitted properly. How do you know if it's the right harness? Well, since there are so many body types, you will have to do some homework. I especially like the fabric-type harness.
Then there are the “no pull” harnesses which supposedly “teach” a dog not to tug or drag you down the sidewalk or lane. (Nobody likes scrapes or bruises . . . or a broken leg.) The problem when this harness comes off, the old pulling behavior is still apparent.
But whatever type of harness you buy, know that it is not 100% secure. A great many dogs have slipped or backed out of their harnesses on their handlers. If you are afraid this might happen to your dog, you might want to consider connecting harness and collar with some type of short snap/lead system. (At the time, there is no commercial product available.)
THE DOWN SIDES
COLLARS
A flat buckle collar is fine for dogs that don’t have narrow heads or heavy necks. Each collar needs to be fitted loosely but not super snug or choking the dog. (You should be able to put two or three fingers between the dog’s neck and the collar, and the collar not slide over the dog's head). And it should pretty much remain set in that position. For puppies/young dogs, you will need to check the fit regularly as they will be growing.
However, a number of my students have told me that the cheaper the collar, the poorer the quality, which means the material doesn’t always hold the buckle adjustment in place for any length of time. Collars have loosened and dogs have pulled out of their collars and “escaped.” Not good.
The martingale or combo collar could also be called an adjustable choker collar, but we don’t want any collar to choke, if properly fitted. A combo collar is not meant to choke. It’s meant to be snug when the dog or you pull on the leash so that the dog is unable to slip or back out of the collar.
These collars are especially good for dogs with narrow heads or thick necks - Border Collies, Greyhounds, Mastiffs, pit bulls, bully breeds, Australian Shepherds, Australian Cattle dogs, German Shepherd Dogs . . . . You get the idea. But don’t discount the smaller breeds. Many of them could use a martingale collar as well.
Regardless of which type of collar you choose, each usually has at least one “D” ring, sometimes two. And people love to hang all sort of things from them - i.d. tags, rabies vaccinations tags, religious medals . . . you name it.
Hanging tags on a collar is something I do NOT recommend, and I don’t even use on my own dogs. The noise can be extremely annoying for the dog and create anxiety. Really. Let me put it this way . . . Think of yourself as wearing earrings that tinkle or clank every time you move, having that rattle in your ear constantly. Now, if you must put tags on your dog’s collar, tape them together so they don't make noise. Better yet, get the i.d. tag type that you can secure to the collar with two rivets. No noise.
HARNESSES
I really like harnesses, especially on pups, but you’ve got to stay on your toes. Those little teeth are sharp and will slice that harness into pieces before you know it. And never leave it on the dog when it comes in or goes to play. More pieces to be collected. I hear it a lot. Basically, if you can supervise or trust your pup not to chew at the harness, take it off! (I recommend do this before something bad happens.)
And let me repeat here - no harness is 100% secure. But getting the right harness can sometimes bring it pretty close. However, here's a good question - if your dog is already backing out of it harness, why is it happening? Whatever it is, it needs to be reshaped into a more desirable behavior. Time to play detective.
I also recommend microchipping your dog regardless of what equipment you decide to use. For us, we microchip all our pets - cats, too (even indoor cats).
But you also need to be aware that there is a big safety issue with any style collar and harness. Your dog should be “naked” in the crate. No collar, no harness. Nothing! Tags, buckles, snaps and “D” rings can and have gotten caught on crate bars, even on the airline style ones. Any crack (intentional or otherwise), crevice, seam or bar is a place part of your dog's equipment can get caught. Dogs have choked to death.
Grates in the floor for heating and cooling, can also snag tags should your dog lay on or by them. Plan ahead. Safety first!
Regardless of which you use, each collar and harness must be fitted properly for each dog.
NOTE:
Living in an area of farms, fields or woods - especially during hunting season - I attach a nice bell to my dog’s harness or collar. I don’t want any hunter thinking we are a deer or a turkey when we are out walking. You might also want to do this when you’re hiking or visiting a large park (like a state or national park) with your dog. The noise is beneficial for a number of reasons.
If my dog escapes, he’ll be easier to find.
The sound alerts other walkers to you and your dog. (My dogs "in training" aren't necessarily happy to see another dog and I like the opportunity/time to move off the trail to make the passing as pleasant as possible.)
It can also warn hunters to be aware that there are people and pets nearby. (I try not to be in those area during that time. Remember, safety first.)
Pups and harnesses
Don’t leave the harness on your dog all the time, especially a puppy or young dog. All they need is five seconds . . . yes, I said five . . . and you will be looking to buy a new one. Even our Freya at three and a half years chewed her last one to bits. It seems she wasn’t comfortable wearing it (it was not her usual one) and Dad forgot to take it off when they came in from playing ball. Most likely, she had a sore spot where it was rubbing.
Best to start your dog’s training early, but do stay away from trying to correct your dog. Reward your pup for doing what’s RIGHT. Ignore the undesirable. Yes, that’s right - ignore it, but first set your dog up for success. And try not to let the problem repeat itself.