I took 2 AR15-22 types and a STG44 22 to the range today. Shot each one about 100 rounds, and I defy anyone to tell which group came from which gun. All three were very accurate. I had one failure to feed in all that shooting, and it was the very first shot attempted. Most likely a magazine issue from a full mag. Keep them clear and use quality ammunition, and you will be very satisfied with your choice regardless of which one you select.
I put 150 rounds through my StG44, the first time to the range, and while it shot the last two mags - 50 rounds - without issue, it probably malfunctioned 20 times in the first 100 rounds; failure to extract, failure to eject, failure to feed; once, all three on a single shot!
My Colt .22 conversion (1911) went 150 without a problem at the same time, but that gun will usually malf once or twice every 100 rounds, as does my 10/22.