My wife and I have been discussing this for a long time and we decided to adopt a mutt that has been abandoned. Although we're not getting a dog immediately, but when we do it'll definitely be a rescue mutt.
These dogs are often abused, neglected and taken in by pricks, like homeless people. Also, they live longer, have less health problems and are just fantastic pets to have. Pure bred are the ones with the health issues because of in-breeding.