I don’t think I could generalise to say any specific breed is smarter than another. Within the breed there is variation, just like in humans. And it also depends on what you mean by smart.
I remember being in new york and many people had tiny poodles which kept their head in the air and didnt interact with other dogs. They might be smart (from their owners perspective as they dont get into trouble) but not smart from a dogs perspective as they wouldnt form packs which helps them hunt (as their ancestors once did).
Dogs used for airport security are smart, and they can be of any breed. What is important is a calm, close bond with their pack leader – you!