A lot of people can't tell the difference, but those who can have a clear preference. Whether it was what you had growing up or just simply the flavor you prefer, Coke and Pepsi have long been rivals striving to be number one.

The advertising campaigns alone cost millions of dollars, trying to compete for your attention and loyalty, but really it's all down to taste.

Back in 2005, Malcolm Gladwell wrote a book called Blink where he figured out the true differences in the flavors.

He found that Pepsi has a citrus based flavor while Coke is characterized by a raisiny-vanilla tang.

He says that because Pepsi has a sweeter citrus taste that it often wins the taste tests, but Coke has a more smooth flavor.

As for the actual ingredients, Pepsi contains more sugar, caffeine and calories while Coke has more sodium.

What do you think, which one is your favorite? Have you ever noticed these flavors before?