Why choose? Well, a number of reasons, but both types are good for you. Here’s a great page that compares P and SP. However, sweet potatoes (SP) are many times higher in vitamin A than regular potatoes (22000 vs 14!!!) SP’s have more calcium and potassium too. Make sure you buy organic and eat the skin of the tuber which contain more fiber and vitamins than the flesh.
A few other potato facts: Purple potatoes contain 4 X more antioxidants than regular white potatoes due to the anthocyanin pigmentation. Also, yams and SPs are not the same, go for the SP. Yams are not as nutritious. One last word – don’t fry them. It pretty much negates the nutritional value by destroying some of the nutrients and adding unnecessary calories. I make un-fries but tossing SP batons in olive oil, salt and rosemary, (NY Times recipe), then in rice flour (*my own addition to make them a little crispier, but you can still make them crispy by slicing them thinner and cooking them hotter – play with it) and laying them on a baking sheet to cook at about 350 – 400F until you can poke them easily with a fork. I turn them over once with tongs. Boom. Delicious and nutritious and when I dip them in ketchup it makes me very happy.