First, the body knows what to do with potatoes. Processed sugar, such as in a snickers bar, is poison, and the body sees it as such.
Besides valuable nutrients, the potato skin contains fiber, thus increases the breakdown time, reducing sugar spikes.
Comparing potatoes to chocolate bars is like comparing orange juice to antifreeze. I would suggest red potatoes locally grown over the mass produced white, including russet, since these contain GMO's.
The problem isn't with potatoes or complex carbs in general, the problem is with simple carbs, such as high fructose corn syrup and processed sugars, cookies, cakes, crackers, and most baked goods. The countries that consume the most corn syrup also have the most diabetes, obesity, and Alzheimers... and America is at the top of the list.