I grew up with both in the house. My brother and Dad preferred Mayo and I couldn't get enough of the Miracle Whip. Now, I prefer Mayo over Miracle Whip for every occasion.
Mix equal amounts of mayo and ketchup for a great french frie dip.
Mayo creams MW on a burger hands down.
MW may have more tang, but it isn't as creamy.
Mayo has flavor, but it is more subtle.