I'd just get the S&W, mags are amazingly easy to load. I thought I read about some problems with the M&P-22 but can't recall. I just don't like the plastic lower though.
I had purchased a .22 dedicated upper from CMMG and I was using their mags. Magazines were a pain to load, just like loading 10/22 mags. I picked the ready-mag adapter
https://www.redi-mag.com/index.php?l...ct_detail&p=52 and have been using S&W magazines. The S&W magazines have a thumb assist that makes the loading so much easier. Sometimes the last round bolt hold open doesn't work, that doesn't bother me much, but I do have one of the very early models that were made.