Hmmmm,
The Walther is a nice pistol it has adjustable sights for both windage and elevation and ambidextrous magazine release both of which is nice. Of course, at the ranges I shoot to practice for self-defense corrections for windage and elevation isn't really necessary. However, I like the newer Walthers made post 2004 as they don't have the trigger gaurds with that little annoying hump along the bottom, the slide is a little improved in texture, and I think the newer ones should have the picatinny rail. However, finding a Walther available in the P99AS variant is going to be a challenge and expensive, unless you get real lucky.
I've fired a Walther P99DAO and didn't like the trigger compared to my M-40. As mentioned the higher bore axis means more muzzle flip and the Steyr in my opinion just has less felt recoil. Two very good pistols and I wouldn't mind having a Walther P99C, but I've only seen them in online and then only in Quick Action. I know that Trigger weight on the P99C is something like 8.8 lbs (heavy).
What I am not impressed by are the Safety Features on the P99 variants and I'm not sure how safe it would be to carry with a round in the chamber? I know my Steyr M-40 is very safe for CCW with a round in the chamber.