As an aside, my S&W M&P .22 (not compact) is bigger than my carry M&P 9c...fit in the same holster though.
So.
Why carry the .22 over something like a 9mm again? Still fuzzy.
I find 9mm pistols too bulky and the recoil to be uncomfortably snappy. The derringer fits nicely in the pocket of my sweatpants.