Ducks and geese have similar down feathers, but goose down is considered the gold standard of down. However, while goose down may have a reputation for being better than duck down, the two are actually not that different, though they do have a couple of superficial distinctions.
Geese have larger down clusters because they’re typically larger animals. That means goose down often has higher fill power than duck down. On the other hand, duck down is more available than goose down because people eat more ducks. That means duck down is less expensive than goose down even though it’s of comparable quality. If you want down pillows, either goose or duck down is a great choice.