I'm rewatching UD and see so many story points lifted wholesale by the DA writers. Mrs Bridges gets romanced by the local tradesman from whom she buys food supplies. It turns out he only wants her cooking, and he don't think she's goodlookin.'
Mrs Patmore is romanced by the local tradesman who supplies her with foodstuffs... But he's only after her cooking.
WWII is announced during a happy summer party in both shows.
The fussy, puffed-up butler. (Hudson/Carson)
The naughty housemaid who fucks around with her betters and gets pregnant, ends up on the streets (Sarah/Ethel) and is later redeemed.
Pretty young privileged girls being WWI nurses (Georgina/Sybil).
Downstairs servant involved in a murder (Alfred/Bates). Homosexual footman (Alfred/Thomas).
Heirs to fortunes dying on the Titanic (Earl of Southwold/the Crawley nephews).
Pretty young woman whose man isn't really in love with her dies of influenza (Hazel/Lavinia)
Young woman goes wild during the Roaring Twenties (Georgina/Rose)
Though plot points are lifted., the character development is so different. Sybil is seen learning how to boil water in the kitchen as her nurse's training, then she gets her halo and puts cool cloths on the foreheads of young men in her home.
Georgina is shown attending a realistic nursing school with strict rules and standards. When she and her friends treat the school as something to rebel against, the nursing school kicks them out. Georgina realizes that she's a shallow and immature young woman and she doesn't like herself much. She begs to be allowed back in, swearing she'll rise to the challenge. They put her on probation and she graduates and gets her ass shipped off to France to nurse men behind the front lines.
Georgina becomes terribly depressed by what she lives through. After the war, she attempts to retrieve her young, carefree, rebellious self by acting out, drinking a lot and behaving decadently. It doesn't quite work out for her. She has to confront more tragedy and learn at least one more lesson about life and the way she is living hers.
Sybil marries the rough hewn chauffeur and quickly dies, attaining sainthood in a flash.
That's the difference between these two shows.