Your question as to which breed is the smartest of all, ends with the existence of the Border Collie. This dog may not be famous for being diminutively adorable and lusciously furred but it still manages to be one of the most favored pets of many homes and farms around the world. Additionally, it doesn't only bests the intellect section but the herding ability section as well for this dog is being considered as the best sheep herding dog in the world.