What you may not know is that many breeds today have very small populations. If some breeds were any other kind of animal they would be considered endangered. You may find it hard to believe, but breeds can become extinct. If you read any histories about dog breeds, you will find lots of references to breeds that are gone now. Countless breeds have become extinct over the centuries. In some cases we have some of their descendants because they contributed to newer breeds, but not always. Some people might not care if particular breeds become extinct, but if you are a fan of a breed, then this might matter to you. From a genetic viewpoint, it’s always good to have a wide selection of dogs that contributed to a breed’s foundation. You never know when it might be necessary to reintroduce some of the genes from an older breed for health reasons. If those breeds are extinct, that’s no longer a possibility.
Every breed can be trained to learn almost every command. However, some breeds learn a lot faster than others - making them a lot easier to train. These highly intelligent breeds pick up a command after only about five or six repetitions, they more often respond on the first time you give the command, and they remember commands even if they are not practiced often. They also learn commands even when the trainer is inexperienced and makes mistakes. So if you do not have a lot of the time to spend dog training, or you are the impatient type who gets frustrated easily, choose a breed which has a high ease of training rating.
If you do not like loose dog hair and do not want to be vacuuming the house every day, then do not buy a high shedding breed. If you own a high shedding dog you will find hair everywhere! Including on your clothes, on your furniture, in your bed, and even in your food. Additionally dogs that have a high shedding rate need to be brushed more often to brush out the dead hair.
When large dogs eliminate, they eliminate a lot more than small dogs. More goes in and more comes out of large breeds. Which is something to keep in mind if your dog will live inside - especially if you live in a high rise apartment and he will have to be litter box trained (there is always going to be more to clean up).