It all depends on your gear. If you have the 4 piece Gronnstalker it is superior, if you use the ashtongue talisman it is vastly superior, if you have a really high raid buffed AP it gets even better (it scales at 20% of your AP, Arcane scales at 15%). Even against high armor targets.
Everyone needs to figure this out and decide for themselves. Even if arcane shot does more damage it does it at a premium, higher mana cost and another cooldown to juggle. Some specs require the extra cooldown to fill GCDs, some do not.