This is the first time I've understood that "Pie vs cake" is a question of two sweet things. I've always assumed *savoury* pie vs cake.
Now that's a really tricky question, because a really good pie - steak and kidney, say, or the wonderful duck and orange ones our local butcher used to make - is a thing of wonder. And obviously cake is good. Usually.
But sweet pie vs sweet cake? I don't really care.
So I've gone for other (chocolate mousse, probably, or maybe even a crêpe beurre sucre, which is the simplest yet most delicious dessert in the universe if done with salty butter).