tish... I guess it's just a matter of personal preference... The couple times I tried fish eating / diving ducks they tasted very strong and fishy. I tried a number of ways of soaking and marinating them and could not get rid of that taste. At least with a mallard, a teal, a widgeon, or some of the other grain eating ducks the meat (breast meat) is somewhat palatable. A well prepared grain duck breast or better yet a Lesser Canadian Honker breast tastes almost like a very rich roast beef.
There's a difference betwween a diving duck (duck) and a merganser ('fish
duck'). Divers (scaup, goldeneye, canvasback, redhead, ring neck) eat celery root, rice, different kinds of vegetation, and some snails, mussels, and freshwater shrimp, but nothing with fins, scales, etc.. Most puddlers eat largely the same kind of things. Mergansers eat minnows. They're a waterfowl, but not a duck..narrow bills and good size teeth.
I usually just roast ducks, unstuffed and salt & pepper, skin on at 325-350. Just
don't overcook. If I put both in front of someone, they can't tell the difference
between a diver and a puddler, other than size (canvasbacks are huge, lesser scaup are smallish, ring necks[aka ringbill, mistakenly called a bluebill, which are scaup] are scrawney like a barnyard rooster, mallards and black ducks are plump, teal dinky, widgeon in between). If I smoke, first
I give them a simple brine overnight, into the pit at 325 for half an hour, reduce heat to finish.