Snickers bars are the losers here when it comes to nutritional value. Why? "Both have peanuts with naturally good fats in them," says Miriam Pappo, R.D., director of the department of clinical nutrition at Montefiore Medical Center in New York City. "But the M&Ms are lower in calories, sugar and sodium, and you get double the fiber." And more fiber means you'll feel fuller longer, reducing the chances of a return trip to the vending machine.