What are you looking to use your gun for? Ruger and Buckmark are entry level target shooting guns, the P22 and Mosquito can't really be regarded as more than plinkers IMO. (certainly fun to shoot if competition is not a factor)
I've shot our club guns including Beretta Neos 6", Ruger Mk II, High Standard Victor (and another HS), S&W 41. I've plinked with a friend's Ruger Mk III and a Walther P22. No experience with the Sig.
For target shooting, the High Standard and S&W 41 were a close match. Heavy, nicely balanced, break like glass trigger, generally more than $500...
The Ruger Mk II/III and Beretta were OK. Both could outshoot me but that may not be saying much. The trigger on the Rugers were so-so, the trigger on the Beretta was terrible IMO. I can't see how it will be possible to change grips on the Beretta if that's an issue. Figure a trigger job into either purchase unless you can find a 2nd hand gun that is already done.
Walther P22. Too small and light to consider as a target gun. Was reliable and fun to shoot. I don't like the look of the compensator but I think its probably prohibited 12(6) in Canada without it.
I was considering a Buckmark Target but for the money, I decided to go another route and buy a 2nd hand higher end .22. I think I would have bought the Buckmark over the Ruger. It fits better in my hand and is much easier to take down for cleaning than the Ruger.
PS an older S&W model K22, 17 or 617 revolver is a hell of a nice gun too. Darned accurate guns with nice triggers. (can shoot double or single action)