Well, it really depends on the breed of duck or chicken for starters. Some breeds of each never (or nearly never) go broody. That being said most broody ducks will not raise more than two clutches a year; whereas, I have had some chicken hens raise 5 or 6 clutches in a year.
Gonna have to go with the chicken, just feels right even though I've only witnessed one of my ducks go broody.
E'aster and Solveig nest share, share the same nest to lay their eggs, and E'aster decided she wanted to go broody. Took over the whole nest and wouldn't let Solvieg near it for about a month. I found it adorable as she built her nest and even shifted it a few inches to the left.
I think in general I'd say chickens, but only from what I've read and heard. I've never owned chickens. There's a huge variation with ducks depending on breed and even the individual hens. Pekins in general usually aren't great mothers, while Khakis and Mallards are, then you have everything in between.
It does kind of make you wonder though... So far that I've researched is that there has been several account of a duck hatching chicken eggs but 90% of the time the duck always rejects the baby chick. Maybe it could be that ducks in general can sense the difference or smell it through the egg shell. It would be interesting to study!
Accidentally I have had ducks hatch chicks - none have survived because they become wet and chilled when their 'mother' goes swimming - not because they are rejected. I have purposely hatched ducklings under chicken hens, and they have been successfully reared by their foster mothers.
Have you ever tried again? But seperated them afterwards so they dont die? Sorry about your chick loss. This may seem off but did you ever get to take a picture of the duck with chicks or your hen with ducklings?
That completely depends on the breeds. For instance i own some of the MOST broody ducks and chicken breeds you can buy. Muscovy and Silkies... they are insane.
Muscovy can and will set 3 clutches and probably more frankly, so they most certainly are a broody duck that could knock out most hens and they can have big clutches... average is about 8 but can go into the teens and twenties.
Silkies are insane they go broody on a rock.
Most duck breeds no longer have the brooding instinct... and even most chickens, i have a few EE"s only one went broody after being a few years old, the others? nope. I own some other chicken breeds that are not broody either.