Man, I wish I could find the material I read a while ago regarding the differences, or lack therefore, between "yams" and "sweet potatoes," at least in the US.

Here's a summary of what I remember. Disclaimer: I can't swear that I remember all of this perfectly, but it's the best I can do.

The two terms ARE used interchangeably for the same root vegetable here in North America. In some cases, in some regions, there is ~ or used to be ~ a meaningful difference between the two.

The word "yam" was at one time used among Louisiana growers, to the exclusion of "sweet potato." Here's where my memory starts to falter: I think I recall something about an effort on the part of Louisiana farmers to copyright or otherwise reserve the word "yam" to distinguish their supposedly superior product from the "sweet potatoes" grown elsewhere. But whatever they may have tried to do, they did not succeed.

In any event, I've never heard anyone use the phrase "yam pie." It's always "sweet potato pie" ~ even when the main ingredient was purchased from a vendor who called it "yam."

I grew up white in New Jersey eating pumpkin pie after all the great holiday dinners, and never even heard of sweet potato pie until adolescence. I probably never tasted one until even later, after finishing collge and moving to New Orleans.

Pumpkin and sweet potato pies both use the same spices, etc., and are pretty much the same color ~ sweet potato just a little browner, pumpkin just slightly orange-er. I find the flavors sufficiently similar to enjoy either one. Sweet potato is a little sweeter and smoother in texture than pumpkin, but since different cooks will use different quantities of sugar/sweetener, and apply different amounts of "elbow grease" to the mixing process, these differences can be very slight.

Therefore, I can't understand anyone claiming to like one of these pies while disliking the other for any culinary reason; that is, for any reason except ethnic solidarity ("our people always make the pie from this vegetable, not the other").

Now, I'll concede one point: sweet potato pie is usually made from fresh yams, or at least whole peeled-and-canned yams. Canned pre-pureed pumpkin is undoubtedly used for many times as many pumpkin pies than is fresh pumpkin. So, insofar as fresh is generally preferable to processed, the typical pumpkin pie could be seen as less desirable than its sweet-potato counterpart.

But then again, I don't discern a critical difference between lime-meringue and lemon-meringue pie, either. Maybe I just don't have a sufficiently discerning palate...