You either misread or you mistypedDid you happen to get a Duality? I'm a bit surprised to hear that the Duality wears larger. What do you think gave you that impression?
While the Sector Field measures 38mm, it's pretty much all dial. The inner rotating bezel of the white (the black wears truer to its size) draws your eyes to the smaller inner dial, making you think it's smaller. The lugs also curves downward so it follows the shape of the wrist more naturally. By comparison the lugs of the Sector are a bit more pronounced and chunkier - suits the style of the watch well but makes the watch look and wear bigger.