The ADG4 is a very simple but effective way to spread the light over a very wide area. While it does diffuse away 2.5 f-stops from the hottest part of the non-diffused direct reflector, it also spreads the light coverage from about 60 degrees to over 180 degrees.
It is not perfectly even on a reflector in order to allow you to still aim the light where you want it the strongest, but it is perfectly even if you mount it "bare bulb" for that purpose.
The ARWD is a silver five inch reflector and it has a shorter neck than the Standard one. That's why it sets further back from the flashtube and broadcasts a wider angle of coverage. This creates a wider broadcast of light within a one f-stop range with the first setting at a wide 80 degrees.
In the first setting it is about as wide as the wider setting of the normal reflector but then it goes to extra wide 95 degrees coverage when it drops back into its dual notches.