You probably won't like this answer, but my choice would be None of the Above.
I have an IR 2131 gun, it works well, does the job on rare occasions that I use it. But, I'm sick of dragging around the damned hose, and the noise. When it does quit (or I'm finally fed up with it), I'm going this way:
I just gave away my 3/8" air ratchet wrench and a 3/8" impact gun to my brother, replaced with a Makita impact gun that I've had for years. I can't remember the last time I had them out of my tool box, they were just in the way.
It won't be long before air-driven impact guns go the way of film cameras.