I've owned a P-22, I own a Mosquito, and My dad has the S&W Bullseye 22 (model escapes me at the moment)
I was looking for something in 22 that would closely approximate a carry gun for training and practice purposes.
P-22: Fun little pocket plinker. Cheap way to shoot so so simulated IDPA courses of fire on private land. if that's your thing.
Con: For my purposes, it had a couple features I'd rather it didn't:
1) Mag disconnect safety. The safety that isn't. You unload and show clear but to do that you have to put a mag in and drop the hammer ... anyone see a problem with that? I do
2) The manual safety is just a hammer block. Everything else on the gun works. Pull the trigger, the hammer falls, just can't hit the firing pin. This caused some confusion for students in Classes when they pulled the trigger and nothing happened.
3) Mag release. The funky under trigger guard kind.
Mosquito:
Has the SIG controls down. Smaller version of similar Sig guns. HAs all the knobs / buttons where they would be on a SIG (only problem is decocker and slide stop are backwards from what I expect coming from a 911)
Con: extractor doesn't always grab hold.
I like the Sig better.
That said, I'd love to own the MkIII, the 22/45. or the S&W