I have one of each and compared side by side, here's what I think:
-Judging by cycling and smoothness of the action, the Walther is a little nicer than the Anschutz 1400/64 action. Anschutz 1700/54 action still king.
-Anschutz has more and better trigger adjustments.
-Fit and finish very close to equal, but if I had to chose, I'd say the Walther by a hair.
-I don't believe there to be much accuracy difference between the two, Anschutz may shoot a touch better but only due to a better adjusted trigger.
-The Walther has much nicer trainer type tangent sights.
-I wouldn't be scared away from the parts issue with the KKJ, just be prepared to pay more, look harder and wait longer for parts. I found aftermarket (non factory) production 10 shot mags and will be picking up two this week. Had to use attheborderstorage.com, ammoclip.com does not ship outside US.
The Walther is definitely the preferred carry along all day rifle, the narrow fore end keeps the rifle light at 5.9lbs.
The main reason I bought my Walther and will keep it - "It is the lightest, and one of the most practical high end bolt action sporters ever made."
Now before everyone jumps down my throat, yes I know the 54 action is superior to the Walther as previously stated. Just remember the lightest 54 sporter with open sights is nearly 2 pounds heavier than the Walther.
As for your decision, it would sure be a lot easier if there were some pics of the KKJ to look at. Provided the KKJ is decent shape, here's my best advice:
"The most sensible thing to do here is buy both, that way you'll truly know what works best for you." Both rifles are keepers anyways
Here's some pics of the one I bought off CGN not too long ago, haven't taken any pics myself yet. These are the original sellers pics. When I got the rifle it appeared new and unfired, built in 1966.