If you prefer a more controlled, less messy environment ducks are likely not going to appeal, ducks NEED water and with that comes mess, mud, wet and many refills of bathing tubs and water drinkers.
On the whole ducks are more hardy, less disease prone than chickens and do a better job of foraging BUT again mess comes right along with that, laying depends on the breed, some actually compare with chickens and some even exceed.
I think chickens are real simple, ducks definitely require more space, more work. I have both here but the ducks exceed the chickens, they are mainly here for pest control(my calls are pets) and wander the farm daily, my chickens some are running in a large yard, others are not(the bantams) now chickens do win the prize for digging they could rival dogs lol but they don't make the mud mess and require the copious amounts of water my ducks do. For all my ducks there are two 50GAL troughs, one 40GAL, one kid pool and several small pans for all the ducks to bathe in that doesn't even get into the water drinkers.
The chickens? HA.. one 3GAL waterer and one pop bottle waterer are their outside choices, yes, we have less chickens but still it's a huge contrast. I enjoy both and will continue to keep both but i think most underestimate the time, work and mess ducks bring forth and i really want people to understand that before entering into the commitment.
Ducks are great fun and have terrific benefits to your property even when combined with chickens but you must be prepared for the basics that are involved.