I say the numbers. Its not about the bullet drop. Its about whether your gun is accurate enough at the distance you are pointing. If you haven't noticed, the number will turn red at a certain distance for each gun. This helps for larger maps, where your gun may not be effective at a distance, and it can tell you when not to waste your time. Besides, on a place like snow valley, if the other person is a sniper, and you shoot at them from an incredible distance with your AK or some other assault rifle, they will notice, turn around, and shoot you before you can get a few hits on them.