I have to vote option 6 because you have not provided any love for Coke Zero or Pepsi Max. Shame on you.
But to be on-topic, there is most definitely a difference in taste between the two products. It is most notable between regular Coke and Pepsi Max, but the two regular products do taste different and even have a different texture in the mouth. The fact I can tell this difference is probably indicative of how much I drink the stuff. Which may be worrying.
I find Coke to be rougher in the mouth, more "sticky" (possibly due to the sugar content), and perhaps more stodgy? I dunno, difficult to describe. Pepsi Max, on the other hand, is smoother, sweeter, and thinner. I'm not great at describing food and drink, so that's the best I can manage, I'm afraid. :3
On a moderately related topic, Pepsi Max is almost king of the soft drinks, only beaten out by Coke Vanilla. I have an especial weakness for the latter.
Kolby Jack said:
I'm quite fond of both, but I would say I prefer Pepsi over Coke, Diet Coke over Diet Pepsi, and here's the tie-breaker, cherry coke over cherry pepsi. Coke's less-sweet flavor allows the cherry taste to come in fully. Cherry pepsi tastes like diabetes in a can. Still good, but MAN, it's almost TOO sweet.
Circumstance dictated I had to drink Pepsi Max Cherry for a few days. It was like drinking liquid marzipan. Not entirely unpleasant, but not an experience I wish to repeat with haste.