I agree with everything about the Welsh Harlequins
I had several breeds before I settled on the WH ducks. Boy am I glad I have them. In our climate, I think ducks are great. I imagine in a wetter climate ducks could be a pain. Sounds counter-intuitive, but our relatively low humidity makes duck mess less messy.
Now as for chickens, I have only chicken sat. I LIKE chickens but I have a mild chicken egg allergy so I didn't get any. But I do think their tendency to scratch up things could be put to good use. Ducks just tend to squash everything down. I am seriously considering a mixed flock if I can manage a coop cheaply.
As for noise, chicken hens are very quiet. My ducks are NOT quiet. They are not obnoxiously noisy, but I have one of those ducks that just quacks her heard off for 10 minutes for no reason. She is calming down though. Like dwd said, it appears to be a teenaged girl thing
If noise was an issue I would get moscovies. They are really quiet, but you do have to either have a covered run or clip wings.
In the garden, if you let ducks in in Spring BEFORE you plant, they will eat up bugs, slugs , and even the bug eggs which will really cut down on your pest population. Also let them lose in the garden after you harvest. During growing season, heck no! They will eat anything green and tender so fast it will make your head spin. You can enclose your plants in poultry wire and let them forage around the plants. That will cut down on the bugs, but do not let them near your unprotected plants!
When I used this set up 2 years ago....
The ducks would nibble off anything that poked through the poultry wire.