Do you just want ducklings? Both the buff and blue swedish should lay 130-180 eggs per year and have fair mothering ability. This all depends on the duck though. I had a runner, who are suppossed to not want to set and be poor mothers, who was excellent. Unless you seperate 1 pair, the male will breed with both. I don't know what color eggs they each will lay but what you could do if I starts to set, put eggs from both (if you can tell them apart) under the setting hen and you will get a variety. won't know what they will look like