I have had both mallard type ducks (pekins and cayugas) and muscovy ducks, and I still have chickens. I can say, hands down, my muscovy ducks are by far my favorite poultry because all of the issues with the mallard type ducks are virtually non-existent with muscovies. and they smell better than chickens, I even keep their water bucket in their coop at night because they never splash it. They'll dunk their heads once in a while to wash out their nostrils, but they never splash it and bring the water out the way my pekins and cayugas did. Their water also doesn't get very dirty because they don't dig around in the mud and then wash their faces in it. When I had mallards, I had to change their water two, three times a day. Now, once a day is enough because it remains clean.
They share their coop and run with three chickens, and they all huddle up at night together in one giant fluffy mass, and they get along very well with them (they're bantams though), although the ducks are definitely more dominant. After getting muscovies, I'm never getting mallard types again, especially the noise reduction was heaven as well. Muscovies are more or less silent, verses my mallards who never seemed to shut up and could call us from an acre back, where their coop was, and still pierce into the master bedroom.
I would definitely go with muscovies if you're thinking of ducks and are used to chickens.
(They also seem to eat much less feed and are happy with foraging for most of their food, wheras my mallards would eat nonstop if I let them.)
Hens go broody when you don’t want them to… and won’t go broody when you do. 
