Crossbows will perform better throughout most of the game if the scout is any good since the AA resetting on skills can approach similar attack speeds. That said, Scatter Shot at the high levels will probably out-scale most of the AoE's given proc bonuses from elemental skills.
In PvP in particular, the crossbow will be much better since AA'ing will be inherently weak, and skills like AIO approach the damage of Murder Shot.