For starters, look at the weight differences between the two pistols, then ask yourself "Why does the S&W M&P weigh so much more?". Then you might wonder how that translates into external and internal design/build differences and durability among other things.

Much like the Walther PK380, the Sig Mosquito feels like a really fun gun to roll around on the rug, jump over couches and play James Bond with. Not that you want to knock around or be rough with any firearm, but it happens and some take such inadvertent rough handling better than others.

Not that all light, plastic guns are cheap and problematic--case in point, FNH's 5-seveN--that's an extremely high quality gun that's shoots the very deadly 5.7X28 round and shoots it virtually flat, with almost no recoil. Albiet, that's a very expensive handgun.

But if I was out in the field for a few days and wanted something I could count on to shoot small game to bring back to camp and feed people, I'd be S&W over the Mosquito all the way. Sig's heard all this and more and they've improved the Mosquito, but it's still not the equal of the S&W M&P22 IMO.

Plus, I think the chances of me having a gun I could keep in good working order long enough to pass onto a younger family member are much higher with the M&P22. The no nonsense lifetime warranty on the S&W, the less expensive magazines and other related gear, make it a no brainer to me.