If you've wondered about sweet potatoes vs. yams, you're not alone! In fact, sweet potatoes are often mislabeled as yams in the grocery store because there is so much confusion. Here are a few key differences: Yams have rougher skin than sweet potatoes. Yams are starchier than sweet potatoes. Yams require more butter, oil, or cream when cooking. Sweet potatoes are much higher in Vitamin C than yams. Yams are much higher in potassium than sweet potatoes. Sweet potatoes are lower in calories than yams because they're less starchy. Sweet potatoes are in the morning glory family and yams are in the grass and palms family.