Hans: In English Heraldry, for those two Emperors, Yes, they are treated SOCIALLY exactly the same, except in their own courts. Some Dukes were Dukes of the Courts (IE, not significant landowners/tennants-in-chief), but a local count had to socially defer to them...
The titles of Nobility have strong cross-cultural equivalencies for most european systems. Emperors at the top, Kingly sovereigns next, Kingly vassals next, Princely Sovereigns, then Princely heirs, then princely vassals, Then Archdukes Soverign, Archdukes Vassal, then Dukes, Then Counts/Earls/Graffs, then Viscounts (where present; I forget the germanic equivalent), then Barons, Then Knights Bannerette, Knights Vassal, Knights Household, Knights Mercenary, then the Grants of Arms, then finally the other Armigers, and last, the remaining non-armigerous gentry.
And, just for good measure, a Patriarch of the Churches ranked as an Emperor, an Archbishop ranked as a King or Duke, a Bishop as a Duke or Count, and an Auxilliary Bishop as a Viscount or Baron. Most Archpriests ranked as a Baron or Knight... and all priests were technically armigers... though the vast majority did not register arms... Deacons were above the gentry and below the armigers, and might hold ecclesiastical heraldry (they are still technically entitled to), but almost none do.
Read AC Fox-Davies.... Loads of fun. The various local indian Vassal kings had right of precedence, but were actually answerable to the Governor General of India, often a count or baron. Likewise Princess Liliokelani was vassal to the Brittish Crown, but was subject to the orders of the Governor General of the Hawaiian Islands; IIRC, the chap wasn't even titled! Similar also the Shaws of the Middle Eastern Protectorates.
Of course, this also has to do with Rank being different from position. Governor was a position, an office. Office authority trumps rank authority.
So the Subsector Duke having lower Soc and more authority is quite simply, based upon historical issues, proof of absolutely nothing other than he addresses the local world's king as "Your Majesty" and officially "Asks" for things... with the subtle threat of deposition for treason if they are not done.