The S&W is about $200 more expensive, but if you are looking for a true .22lr AR trainer you have to pick the S&W in this head to head. I dont like where the safety is located at on the Mossberg, and as RTB notes:
The Mossberg AR-22 is a different animal altogether. Unlike the M&P 15-22 the AR-22 was NOT designed from the ground up to be a ".22LR Trainer"; rather Mossberg took their successful 702 Plinkster design and placed a cosmetic shell over it to emulate the 'look' of an AR-15. The result is that the rifle has no controls even remotely similar to an AR-15 and is a pain to disassemble for maintenace.
