Have owned both(my Beretta was the 84 with a higher cap. magazine). Both are all metal guns, large these days for their caliber. Both are very well made, and easier to handle and hit with compared to the newer micro sized 380's, like the Ruger LCP or Keltec. In my opinion, the Beretta has a better trigger, and is more accurate, as well as more reliable with hollowpoints, compared to the Walther. Also liked the feel of the grip on the 84 better, though being the high cap version of the 85, it was a slightly wider double stack frame.. Also, the Walther was a pre-S&W gun, so feeding with hollow points may have improved. I used to get hammer bite with the Walther, something to consider if you have large hands.
How a gun fits in your hand is important, as is trigger and controllability, and both these guns are a step above the newer micros in that regard, making fast and accurate hits easier. My personal choice would be the Beretta, though frankly, for the size of either, I would probably be looking at a 9mm at that point, like the Glock 26 or the S&W M&Pc.
Larry