On the Paleo diet, Loren Cordain recommends not eating white potatoes because they are members of a family of plants (nightshades) that contain saponins. He believes these saponins can exacerbate any leaky gut problems. You might go look at Loren Cordain's blog to see if he has more information about that if you are interested.
Since sweet potatoes are not nightshades and don't have saponins, they're considered safer to eat. The Primal Blueprint gets a lot of its ideas from paleo but also from elsewhere. The Primal Blueprint is also less strict about what should be avoided. I think Mark still recommends not eating white potatoes. He loves purple sweet potatoes.
Many people around here do eat white potatoes. There's a silly crash diet that eats only white potatoes and nothing else. Then there are people like me who just eat them now and then. I think sweet potatoes are better, but now and then white potatoes hit the spot.
Female, 5'3", 50, Max squat: 202.5lbs. Max deadlift: 225 x 3.