White rice is considered pretty much of a null food. It won't hurt most people, but it's not nutrient rich. It is however a nice way to inexpensively increase calories or round out some dishes. If you plug both white potato and sweet potato into a tracker, the biggest difference you'll see is the VitA boost from the sweet and a bit more protein in the white.
IMO both can be used in moderation on a regular basis. A quarter cup (dry) white rice has about 34 grams of carb (changes depending on type of rice). A 10 oz white potato has about 45 grams of carb. So, even if you're staying at less than 100 grams of carbs per day (and not everyone has that goal), you can easily fit rice and potatoes into your meals as long as you're not eating piles of the stuff.
ETA: I always forget about the nightshade issue because it's not an issue for me. White potatoes are nightshades.
Last edited by JoanieL; 10-21-2013 at 06:32 AM.
"Right is right, even if no one is doing it; wrong is wrong, even if everyone is doing it." - St. Augustine