Which ones a better snack: a single serving size of 99% cacao dark chocolate or a single serving of fruit?

Fruit: 99% Cacao is certainly better than mild chocolate or other sweets, but it does not beat a fresh fruit. Fresh fruits have loads of other nutrients, fiber, antioxidants (cacao has some too), and will keep you full for longer. I recommend apples and pears because they have a good blend of soluble and insoluble fiber and it is easy to measure out a serving; one.