From my warped world view, cake is merely a frosting delivery system. Most cake is dry, tasteless, and, quite frankly, a waste of calories. Thankfully it has sugar in it because that's really it's only redeeming quality. There's not a lot, in my less than humble opinion, of variety in cake.
Pie, however, is just amazing. First, there is the glorious texture of really good crust. Mind you, it doesn't have to be regular run-of-the-mill pie crust. It can be graham cracker or cookie crust. You can add nuts, or other types of tastes and textures. Then there's the question of one crust or two?
Then there are fillings. Fruit, cream, or even, if you're so inclined, meat. If given a choice, I doubt I could decide between lemon meringue and key lime. Such exquisite flavors! However, on another day, what's better than a warm apple pie, topped with caramel and ice cream? Yet, then there is the thrilling tastes of a chocolate, banana or coconut cream pie. Sigh. Heaven.
I'm sure that someone can make a case for cake. For me, though, nothing will beat the variety and glory of a good pie. And if it's a bad pie, you top it with ice cream!