That's because it is sweeter. They use more sug... er, high-fructose corn syrup in Pepsi than in Coke. Not a lot more, but enough to give it a sweeter taste.

coke fan... will drink pepsi in an emergency

I favor Pepsi products, but that's only because Mountain Dew is a Pepsi product, and for me, Mountain Dew > all.
However, since I live in Georgia (read: birthplace/capital of Coke), I have to settle for Sprite most of the time I eat out. Sprite isn't bad or anything-I like it-but it just isn't Mountain Dew.

Don't like Vault much? (The current Coke equivalent of Mountain Dew, that replaced Mello Yello.) I too live in GA and most of the fast-food joints that serve the Coke line do have Vault. Less so for sit-down restaurants though.

Vault is not the equivalent of Mountain Dew, Surge was. Vault is in a class of it's own.

Vault is no Mountain Dew substitute. Mello Yello was no Mountain Dew substitute. The difference, however, is that Vault doesn't seem to be trying to imitate Mountain Dew in favor of offering a new flavor, whereas Mello Yello was a poor imitation at best.
Nevertheless, I couldn't quite get used to Vault. It's a bit odd.

Because it's that bad?

OMFG NOOBS! Coke kicks pepsis ass! It's open sores and runs linux and uses OSX as its window manager and it uses AMD and ... ps3... wii... shit... I'm out of fanboy things to say :( Help!

fold or crunch?

Coke has open sores?? Ewww, glad I don't drink the near pepsi-identical swill

Depends how long it's been since I washed my underpants

I'm a Coke-supporter. Never really liked Pepsi.

Coke. I fell in love with it when I tried Vanilla Coke, then found I also rather liked regular (because clearly I am a good person). I don't like Pepsi as much because it is sweeter, (and also because I do not enjoy sucking from the teats of Satan). Before that I didn't really have a favorite (not that this excuses foul Pepsi-lovers). Though I've always been fond of cream soda and of course root beer, especially the A&W brand of both.
Lately, however, I have decided to stay away from caffine. I finally put 2+2 together and realised it was having a very negative effect on me, so much so that I am going to fully treat it like a drug and not a food from now on. If I do drink caffine again, like with any other drug it will be because of a need (combat tiredness or whatnot) and not something I'll simply consume casually anymore. I'm not trying to preach that caffine is evil or anything, this is just my experience with my own body's reactions to it.
Lastly: Pepsi kicks puppies, puts pepper on the noses of kittens. Hitler, Godwin, etc.

I prefer coke, it just tastes less acidic to me and all the other flavors are pure awesome, vanilla, cherry, etc.
I freaking love Vault but its been hard to find lately.