This one is hard because most of the stuff Arn did was back in the day, and the stuff that Austin was known for came in the Attitude era. Different qualifications were needed in both eras.
WHen I saw this match up, the only thing that came to my mind was the feud between The Hollywood Blondes and the Horsemen. I believe this was in 1993 in WCW, I may be wrong on the year. If you haven't seen these promos, you need to look them up.
Let me put it clearly, you had 4 of the best stick men in the business. Brian Pillman (AFTER his "flyin" bullshit), Stunning Steve (while not quite stone cold, he still had some skills), Ric Flair (no need for description here), and AA. All four could talk, wrestle, and entertain.
But if you watch the clips, as good as Steve is today, he just wasn't as good as the other three in that feud. Granted, the other three were the greatest of all time.
Austin has the most memorable interviews of the two (check the interview he did in ECW talking about Bischoff firing him, that is the most played promo on my ipod,) but Arn had the more effective ones.
Austin created Austin 3:16, Arn created the name The Four Horsemen. Which I have to say is kind of a wash.
As a result of that Blondes - Horsemen feud, I'm going with the Enforcer.