The answer depends on where you're hunting. In my experience when hunting water, you get more ducks with an occasional goose. Ducks will fly in and out from water holes during the day and geese prefer to feed in the fields during the daylight hours.
There are times when both will fly into your setup on water.

Andthe bigger your decoy spread the better. Get at least 2 dozen decoys and split them on the water with a hole in the middle where you want them to land. If you bunch them up, they will land on the outside edges making for longer shots.

Good Luck