I would have to say, pepsi. Coke tends to leave a nasty coating of something on my teeth that makes me want to grind them down to the roots. Besides. Pepsi gets the sexy women to advertise. Coke gets Abercrombie rejects.
I'd choose Pepsi myself if it was a race of the original Pepsi or Coke, but when it comes down to "mods" of the drinks, ie. Vanilla Coke, Coke would win because pepsi is like microsoft, they suck coming out with anything new