There is a family recipe which calls for either canned or fresh sweet potatoes or yams. Is there any practical difference in preparation? Sweetness level? Does the cooking process matter (it's a baked pan of mashed potatoes)?
In preparation, there shouldn't be differences beyond the obvious (cook the fresh, drain the canned, etc), but the flavor will be different. Canned yams are frequently packed in syrup, which will make them very sweet. Some people think that canned goods taste "like can" as well. On the other side, the method used to cook the yams will effect the texture and flavor (boiled will have less flavor and be softer than roasted, etc).