You will consistently get good results when you bake sweet potatoes at 425ºF. Potatoes baked at 400ºF tend to have a slightly more stringy, less creamy interior, even if you add 10 minutes to the baking time. Potatoes baked at 450ºF start to blacken on the outside of the potato, and the interior results didn't seem much better when compared to the potatoes baked at 425ºF, so the middle-temperature range will give you the best results.