I use what ever is available. Adding sour cream, yogurt, hvy cream, even herbed cream cheese thinned with water, they all add a tenderness to the scambled eggs or omelet, each adds a distinct layer to the taste. The more acidic the addition (sour cream, yogurt) the more tender.
12 yr old grandson considers the scramble with yogurt a gourmet item that only his grandma has to secret to. Oh, the power, the satisfaction of being so perfect in his eyes!