I cannot comment on any AR 5.56 platforms, but I have had a Kel Tec PLR 16 for many years and it's been a reliable and accurate weapon. OAL 18.5", approx cost out the door is $500.
Another 5.56 pistol I have recently (less than a year) is a C93. This is very unique as it's like an affordable HK, so mostly just a cool factor. It has also been very accurate and reliable as well. OAL 20", Approx cost out the door $700.
Good luck with what you choose!
Here's are mine and they've been good for me.