While they are somewhat interchangeable, they have their own attributes. For example, prune puree's dark color may not be appropriate for a light-colored cake, where applesauce would be a much better choice. Pumpkin or squash puree is also a favorite of bakers. The tradition of bobbing for apples on Halloween may have originated with an ancient Rome autumn festival honoring Pomona, the goddess of fruit.
Apples are so versatile and can be used in so many baking recipes and desserts.
When baking pies with apples, it's a good idea to mix a few varieties for even better flavor. Always wash, peel and core for use in recipes. Apples for baking need to be washed and cored, and those for candy apples just need to be washed and dried. Varieties are regional, so the availability of types will vary depending upon where you live. I'd love to hear from others on what their favorites are, too.