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.
Most all dogs will get along well with children if they are raised with them. However, some breeds have a protective streak in them and may become aggressive with children who get to close at meal time (although this should not be tolerated), or aggressive with children they have never met. These breeds will likely see the children as being underneath themselves in the "pack order" and may try to dominate them.
That’s why we need breeders of purebred dogs today. People who breed to preserve dog breeds are usually hobbyists. They may participate in dog shows or companion/performance events with their dogs. The dogs that they can’t keep are usually placed in pet homes. Yet cities and state legislatures are passing laws that can make it virtually impossible for smaller breeders to continue this important work.