Both erode the teeth more apparently than any other soda in my opinion (except maybe Sprite), and I don't particularly like either soda. In fact, I'd rather have Dr.Pepper if I'm going to have a cola at all; Coke makes my teeth feel weird and Pepsi makes my stomach bloat very easily.
For the sake of the thread title, though, I think I prefer Pepsi to Coke, but I haven't had Pepsi in such a long time - to the point where comparing the two would be almost impossible.
Both. I actually don't taste much of a difference between Coke and Pepsi. My Marketing teacher last year used to go off on how it amazed her that some people could actually like Coke more than Pepsi, and when I told her that there wasn't much difference between the two she was speechless, lol.
I will drink any soda. I like every single one of them. Every one that I've tasted so far, at least... So, when it comes down to Coke vs Pepsi, I choose both.