I can assure you, it tastes different... or at least Mexican Cokes in glass bottles do. Go find you one and drink it. It's substantially different and better. It's sooooo good.
According to the WSJ this is because "Food scientists have noted subtle differences between the sweeteners: High-fructose corn syrup’s sweetness intensity tends to peak earlier, enhancing fruit and spice flavors, while sugar’s profile is broader and lingers."