Dogs who have been uprooted from their happy homes or have not had the best start in life are more likely to bond very completely and deeply with their new people. Those who have lost their families through death, divorce or lifestyle change go through a terrible mourning process. But, once attached to a new loving family, they seem to want to please as much as possible to make sure they are never homeless again. Those dogs that are just learning about the good life and good people seem to bond even deeper. They know what life on the streets, life on the end of a chain, or worse is all about, and they revel and blossom in a nurturing, loving environment.
Most rescues make exceptionally affectionate and attentive pets and extremely loyal companions.
Unfortunately, many folks think pets that end up in rescue are all genetically and behaviorally inferior. Rescue a cat and get a cuddler who will purr as you pet.