The difference between fairy cake and muffin/cupcake tins is the fact that muffin/cupcake tins are larger in size and depth. Therefore, when baking please ensure you use the correct tin or tray. Below is a picture of both a fairy cake and muffin/cupcake tin. The silver one is the one used to bake small fairy cakes and the black one is used to bake/cupcakes muffins.
Fairy cakes are usually drizzled with liquid icing and sprinkles and the muffin/cupcakes have a range of flavours and are covered with a large whipped topping.