I wouldn't get a Walther P22, if you want a quality Walther .22 pistol get the Walther PPQ 22. There is a significant difference in quality, the P22 is built at the Umerex, Arnsberg plant, where the PPQ 22 is built at the existing Walther plant in Ulm, alongside there vaunted PPQ 9, 40, 45's. Walther is now owned by Umerex, but the way I understand it the Ulm plant still utilizes much of the existing equipment and manpower that is known for quality.
I purchased a Walther PPQ 22, based off the quite poor reputation of the P22. There are people who get the P22 to run right, and high velocity ammo helps, but I don't like to go 2/3's the way when I can just save a little more and have a better, more reliable product.
Based of the two choices given, I would get the SR22 even at the added cost.