Here's a thread I did awhile ago comparing the P22 and the Mosquito. There are lots of pictures, and they keep popping up as you go through the whole thread:
http://www.canadiangunnutz.com/forum/showthread.php?t=132068&highlight=P22+Mosquito
I have owned both guns for some time now, and have shot them both alot. The Walther is the better gun ... providing that you at least get rid of the "compensator" and move the front sight to the front of the slide. If you don't do that, and you try to make that compensator thing work, then it is the worse of the two guns.
The Walther is a better design overall IMHO. The plastic wrapped barrel of the SIG is kinda weird. The Walther gets better with age (by which I mean it is getting more reliable as it sees more use). The SIG... not really.
The Walther can be fired much faster than the SIG.. or pretty much any other .22LR pistol. Very short light SA trigger. Very fun to shoot. The SIG is fun too... but it's neither a rapid blaster... nor is it a target pistol... so...
The guns are about the same in terms of accuracy. I have gone back and forth on which one is more accurate. Both are fixed barrel designs and both are pretty decent on accuracy for what they are (not target pistols).
P22 break? No, not the newer ones anyway. I've got around 20,000 rounds through mine (in 18 months) and it is still getting better with age. I have many times shot 500 rounds in an afternoon. No problem with any of the springs, extractor, ejector... nothing. And that is with shooting every kind of ammo from cruddy American Eagle to Stinger, Velocitor and Mini-Mag.
If I were going to only buy one, it would clearly be the P22. Like my USP 9mm, my P22 comes to the range just about every single weekend. Mosquito gets invited maybe once a month these days... and I bought it after I got the P22.
For what it's worth, my girlfriend has a Ruger 22/45 and has shot the P22 and the Mosquito a lot too. The Ruger is more accurate (hers is a bull barrel... not that it really matters much though. The Ruger has so little movement in the design) but her favorite of the three is the P22. The P22 is just fun to shoot for some reason.
P22 will actually shoot pretty accurate if you take your time and concentrate. Sometimes we stand up used shotgun shells on this log at the range that is 15 yards out. Last time we did that, I knocked five of them down in my first seven shots. It's hard to ask for more than that from something that is supposed to mimic the look and feel of a full-sized pistol... just on a 3/4 scale.
Love that P22. Just remember to keep it clean... and don't use that damn compensator!
