Coke Zero versus Diet Coke versus Diet Pepsi --help!!

[Orel Hershiser]

Ok, so I drink Diet Pepsi because I like it better than diet Coke. I have recently tried Coke Zero,though, and like it better that Diet Pepsi or Diet Coke.

My question, how is this possible? Aren't Coke Zero and Diet Coke the same thing, just marketed differently?? Why do they taste different.

NOTE: All the above have caffiene, so I'm not referring to any caffiene free colas.