difference between cupcake and muffin
There might be some technical differences that a cook could tell us
about, but from the consumer's point of view, the difference seems
to be that a cupcake really is like a miniature cake: light in
weight, sweet, and often covered with icing and
decorations.
It tends to be not too tall because it's texture isn't strong
enough to allow for a very tall structure. It's always made with
white flour as far as I know.
cupcake
A muffin is significantly heavier in texture and also in weight;
with its cohesiveness, it can contain fruit, nuts or chocolate
chips, which are not common in cupcakes.
It is never iced and need not be particularly sweet. It can be made
with ingredients as heavy as bran, and can be rather tall and have
a large overhanging rim that doesn't threaten to fall off. (The
cupcake also has a rim, but it is rather delicate and not too
large.)
If you threw a cupcake against the wall, you would hear something
of a "poof!" If you threw a muffin, you would hear a
"thud!"
A muffin goes with coffee, a cupcake with tea. (That's a rather
controversial statement, so perhaps this discussion should be moved
to the controversial topics zone.)
Sociologically, a muffin is everyday living, whereas a cupcake is
"we're getting fancy."
Theoretically, a man could say, "hey honey" to his waitress while
he was chewing on a muffin, but with cupcake in his mouth he could
only say, "my dear."
If you were writing a novel, it would be a gross literary error to
substitute a cupcake for a muffin.