I have both. (For that matter I've got the Arbiter, Reaper, 30P1 and 30PS).
Arbiter is lighter and honestly I think the tone sounds just a bit better (but not much). I like the SAS thread over mount.
However I use my 30P1 more on my 308 bolt guns. I don't have accuracy issues with either but I know there was some talk that there were some issues with the SAS.
My biggest concern about buying another SAS can is lack of customer support from the factory. Mile High is the only dealer that I know of but I want to be able to talk the guy who makes the thing. I know that I can email Zak (or PM/Post here) and get a near immediate response. If I have a baffle strike, I know who its going back to - with the SAS I'm not sure…