If by Walther you mean the Colt/Umarex, I have shot them both. Accuracy is about the same, and both are good (and neither is a bullseye pistol).
The Colt does not field strip like a 1911. The barrel is an integral part of a riser that's cast into the frame. I suspect that actually helps accuracy, but it's too non-1911 for my taste.
M1911.org tested both in their e-zine awhile back ...
I also tried the Kimber Rimfire, but it's ALL aluminum and doesn't weigh enough to feel like you're shooting a real gun. I finally decided to go with a basic conversion kit and use it on a steel 1911 receiver so there's some weight. Kimber sells a conversion kit as well as the complete pistol. Accuracy is very good -- but it only comes with adjustable rear sights, which isn't strictly "GI" in appearance.
I see you are in Italy. I'm not certain, but I believe there are a couple of .22 caliber 1911 conversions available in Europe that are not sold in the U.S. Have you investigated conversions?