Yes both of those guns well take ducks and are good starter guns. A a kid I killed sevreal mallard ducks and pheasents with my trusty HR single 20ga.If possable you might want to look at 12ga you might get better results. The 20 ga is a good choice but it has its limits. I could be wrong (havent hunted ducks in 5 years) And I useally am but looking around stores and shops I noticed that some 12ga shells were cheaper than 20ga and easyer to find. Best of luck to you and have fun.
20 Ga. is fine, just live with the limitations of a smaller shot load than a 12. I have not hunted ducks in years, but, I took many as a child with a .410 and 20ga; the ducks could not tell the difference.
Please do pattern your gunswith the type of shot you intend to hunt with before you go out for the first hunt; you may have to try a few different loads or choke combinations (provided you have screw in chokes) to find what works for you. Maybe try a few rounds of skeet.