Remember that the duke is not necessarily the lord of the city anymore.
Trust me, people IC won't let me forget. Yet, in spite of that odd change most Lords of Cities remain as Duke's. And when that's the case (as it is in the majority of cases), where's all that fealty and stuff? Not seeing it, right now.
This is kind of an example of one of those areas where Tom wishes the game was one way, but the players just don't play it that way.
Geronus hit the nail on the head. Unless you're going to contradict the answers Tim gave, nothing changes for 99% of people and situations IC.
And yeah, being Duke of a city halfway sucks if you can be Duke of a townsland. Genius
Finn.