The Ruger is a really good gun, I've shot an older MKI or MkII, really liked it, grip angle was a little different but not bad.
The Walther .22 is not bad, my cousin has one. His seemed to be a little picky on ammo, not too bad. A little smaller feeling for me..
Another cousin has the newer Ruger, I have not been able to shoot it, but it looks and feels real good, also a little small feeling.
I went with the S&W 22A and love it. It feels real good in my hand and shoots great. The take down is not the easiest, but eh, it's not too bad. I think you can pick one up for like $200 used or ~ $250 new. For some cheap .22 fun you can't beat it. It's also not picky on ammo, I've only used the cheapest bulk stuff I can find. Oh yeah, it's also got an integrated rail on the slide for if you decide to scope it or something. That's pretty cool, you may not want to right now, but it's a cool option.
That's another point, if you have to use higher end ammo, like Stingers and Mini-Mags doesn't that kinda negate the purpose of buying a .22?