I'm in the same boat, I want a service style .22 and started looking at the Mosquito again and the M&P. I figured maybe by now they have fixed the Mosquito's issues. I still see mixed reviews on it though, much better than a few years ago but certainly not 100%. I see great reviews on the M&P so far though and I do like the feel of it. I'm leaning towards the M&P22 myself but am still open on the decision (I already have a NEOS and a 22A and my son has a Buckmark ... all are good guns but none have a service type of feel to them).
One thing for me right now, the slide on the M&P is machined aluminum and seems to be of good quality. Not sure what the slide on the Mosquito is but I've heard it marks up easily.
597 VTR, because there's so many cans and so little time!