Its actually both drop and reach...I have experimented extensively. Greater reach changes the position of the traps which can cause more pressure on the base of the neck. A wide handlebar also promotes holding up one's torso with musculature versus skelton which can also accelerate neck pain for those predisposed. I always think about the great Eddy Merckx when it comes to chasing pain after his accident as he set the most notable example. No single position is ideal or sufficient. Changing positons is what brings relief albeit only temporarily.