I've never liked Pepsi
And my taste-based preference proves itself right on another, unexpected level: Pepsi is run by a bunch of whiners.
In my opinion, the people who actually care about performance out of their sports drink (versus using it a simple hangover cure) probably know enough to know more calories are generally better as far as hard-core performance goes.
For those of us looking to just cut calories, though, it's pretty convincing. I mean, more calories makes you gain weight -- so it's not so terribly misleading as Pepsi would have you believe. I think Pepsi's sore now that it realizes the Amish make for better commercials than Britney Spears.
And anyway, sports drinks taste nasty. I prefer unsweetened iced tea, personally.