what are advantages/disadvantages of creating "Duchy" titles?

[MadGelo]

I can create like 8 of them atm, but i'v read somewhere that you shouldn't do that.

thx

 

[jordarkelf]

For existing dukes:
advantages:
-prestige
-vassals can be happier since you have the right of rule
-closer to being able to form a kingdom

disadvantages:
-if using gavelkind, you lose parts of your realm if you have multiple sons on succession

For kings:
pos:
-fewer vassals, less chance of revolts
-can use some of them to give to children to prop up prestige for them
neg:
-if using elective law, having more than two for yourself makes your vassals angry
-powerful dukes will be a threat to your rule
-vassals will demand the ducal title for their area if you own it.

 

[Zhetone]

What I usually do is create them and dispense them to trusted vassals to keep the more rowdy ones in line. They also consolidate rule and keep things nice, orderly, and somewhat more centralized, which I quite like. Vassals can sometimes create ducal titles themselves, but I'd rather be in charge of who has what.

 

[dorukdorucu]

Having more than 2 angers your vassals, also if you have more than 1 son(or child, for cognatic succession) they will split between your children while running gavelkind succession. You also get less taxes and levies since each vassal keeps some of them for themselves. However you also get less direct vassals to deal with, so you can possibly get +100 relations with each one, in the end getting back the levies and taxes.
If you have elective law, and hold less than %50 duke titles, someone you don't like can be elected. However, on the other hand 2 county duchies and usually even 3 county ones get created, so better create them yourself for prestige and give them to people who like you.