You can't go wrong with either one.
The new design Spectre 2 is a great improvement over the Spectre 1 in that the baffles completely contain the blast and just and really not much contacts the serialized tube.
The only real advantage I see with the Sparrow over the Spectre 2 is that the Sparrow has nothing threaded in the serialized tube so there is no thread to mess up on the external tube. That way if the internals of the can get messed up somehow, there is minimal chance that the serialized portion will sustain any damage.
The front cap and the back cap both thread directly into the serialized tube on the Spectre 2. If those threads get messed up, you would need a new can and a new $200 stamp.
I own a Spectre 1, Element, Spectre 2 and a Sparrow SS.