Well, I like both. Let me explain:
I'd rather drink a diet Coke, than a diet Pepsi.
I'd drink either Coke or Pepsi when it's regular. (AKA not diet, caffine free, etc..)
I'd rather drink a flavoured Pepsi than a flavoured Coke.
Although, I'm a Sprite/Sierra Mist person myself.
...Root Beer is up there on the list, too.