Sweet potatoes are around one third lower in calories and carbohydrates than regular white potatoes, which may be good for some, but they're also lower in fibre and protein which is not so advantageous.
Sweet potatoes generally score lower on the GI index but this varies with cooking method and whether the skin is consumed. Eating either type boiled, complete with the skin is the best option GI wise.
In terms of micronutrients they both supply B vitamins, magnesium and potassium. However, it's the orange flesh sweet potatoes that really take the lead with around 8000 times the amount of beta carotene, a form of vitamin A that's an antioxidant that may help to regulate the immune system and control inflammation. As with other colourful fruit and vegetables, sweet potatoes with purple skin or orange flesh are also higher in beneficial phytonutrients.
Both regular white potato and sweet potato can feature as part of a healthy balanced diet but think about preparation and cooking methods and of course what you serve with your potatoes to really maximise the nutritional benefits.