When was the last time you had a soft drink that was "naturally sweetened?" High fructose corn syrup is NOT natural, regardless of what the corn growers try to tell you.
That said, I enjoy both Coke Zero and Sprite Zero, but I grew up drinking Pepsi Cola, before diet drinks and when all sodas were sweetened with sugar, and I really prefer Pepsi Max. It tastes like what I remember Pepsi tasting like.