As a baker it's frustrating when cupcakes and muffins get confused. They're not the same thing, and whilst both are made from flour, eggs, butter, sugar, and milk, that's where the similarity should end... if they're made properly! Common misconceptions about muffins vs cupcakes are:
"Muffins are ugly cupcakes"
"Cupcakes and muffins are the same thing"
"Muffins are just cupcakes with icing on them"
"Cupcakes are like fairy cakes; muffins are just big cupcakes"
No! Muffins and cupcakes are not the same, the ratio of ingredients and method of mixing them are completely different.
Muffins should be well-risen, moist, with more density to it. Sometimes they have fruit in them, sometimes chocolate, marshmallows. Often you will find some of the flour has been substituted for oats, cornmeal, and even polenta! Muffins should not be iced, although they do sometimes come filled. Our muffins are lovely and big and we know (from being expert makers of them) that the ratio of ingredients and the technique used to mix, will result in an entirely different baked item at the end. You don't cream your butter and sugar together for a muffins. Muffins are popular for breakfast, and can be eaten every single day without feeling too glutinous. You can also make them savoury, by omitting the sugar and using ingredients like cheese instead.
Cupcakes should be light and airy, yet moist; topped with icing. Generally they're smaller and sweeter than muffins (Wraggamuffins make those lush big muffins, so our cupcakes are definitely smaller). The basic ingredients are the same, but the quantity of sugar and butter is higher; both being creamed together before adding the other ingredients, whereas the fat is usually in liquid form for a muffin. cupcakes sponge should have a definite "cakeyness" to it which muffins just don't have. Also there should be no crusting on the top of the sponge. Usually a cupcake is decorated with fondant or buttercream icing; they're more fancy, making them a treat rather than an every day food.