Coke. Competing soft-drinks are better than Pepsi's, and they have a lot of other great stuff as well. Five Alive, FUZE? Yum.
Coke does lose its freshness much quicker than Pepsi, I have noticed. Which sucks if you don't intend drinking the whole bottle, however big it may be. Pepsi keeps its taste longer. However, that's either good or bad depending on how you look at it. Perhaps less perservatives in Coca-Cola? Also, it has a much crisper taste fresh, and when it's cold, it tingles all the way down your throat. It's the best.
I'll start loving Pepsi again when they bring back Pepsi Blue.