Shuriken's base damage is 1d3 compared to throwing daggers 1d4 which also have higher critical of 19-20 rather than just 20.
This may actually already be in but shuriken should reload a LOT faster than daggers to compensate (like it is in pnp). Given that it's also an exotic weapon (and only free to monks and drow) it should have some basic advantages over the other weapons.