What makes a dog a good pet has more to do with how much time you spend working with the dog to train it and socialize it, not where you get it. If the dog spends most of the day alone and is stuck in a house or back yard with out much contact with you, or exercise and training it won't be a good pet. A well behaved dog, that is a joy to be around takes a lot of daily time and patients. The upside of getting a dog from a shelter is that you will get a dog that has been checked over by a vet, to make sure it is healthy, has had it's immunizations and has been spayed or neutered and hopefully temperament checked, and you will be saving a dog's life. Usually shelter dogs don't cost as much as a pet store dog. The downside of a shelter pet is that it may have some issues from it's past life that you may not be able or want to deal with. Many of the shelter dogs have been abused or neglected. If you are a patient person, you may enjoy a challenge of helping a dog with issues and giving it a good, forever home. Pet Store dogs cost a lot and then you have to take them to the vet to make sure they are healthy and get them spayed or neutered and get their immunizations, all of which will be an added expense. Pet Store dogs are very often from Puppy Mills, where the puppies are born from female dogs that are kept in tiny cages,and do nothing but have puppies all of their life. No care is given to the physical or genetic health of the parents of the puppies and so you can get a puppy that will be more likely to get ailments, such as hip displaysia, epilepsy, eye problems etc. Many times puppies come from pet stores with ear mites and kennel cough as well. If you are going to buy a puppy from somebody and you want a purebred dog, you would do better to buy from a reputable breeder and not a pet store. You can go to the American Kennel Club website and find breeders, of the breed of dog that you want.

Temperament is the real key to what dog will make a great companion animal. As shared, this is often compromised with Pet Store puppies, because the vast majority do come from Puppy Mills. Puppy Mills have NO interest in anything but producing as many live puppies as they can as fast as possible. They overbreed, their dogs and bitches, and they take no consideration for any qualities the dogs have or what traits are in the bloodlines that will show up in the resulting puppies. I've seen puppies, cute as can be, that were stark raving MAD...not angry...crazy...would not be capable of learning or living in a normal family setting at all...they had gone mad. ScrubJay summed it up beautifully here.