Sponge cakes are lighter and depend on eggs for texture, but butter cakes are rich and thick because of butter.
While sponge cakes employ beaten eggs folded into flour, butter cakes are made by creaming butter and sugar.
While sponge cakes are light and fluffy, butter cakes are supple and moist.
Sponge cakes are lighter and more neutral in flavor, whereas butter cakes have a deep, buttery flavor.
Sponge cakes are lighter and perfect for rolling or delicate desserts, whereas butter cakes are firmer and great for layers.