As the eatin' season begins, it seems to me that someone out there can discuss the difference between pumpkin pie and sweet potato pie. I've only had SP pie once, a good while back. But it seems to me that they're both basically the same thing, a custard with cooked, pureed flesh and similar spicing, which is variations on cinnamon/ginger/nutmeg/mace. But that's only a theoretical description. Lots of folks seem to prefer one to the other. Help me out here. What's the difference? Why do you prefer one to the other?