Having flown the Carenado CJ2 extensively for about a year now, with and without the mod, I would say the main issue with the Carenado PL21 is it's lack of functionality compared to the real PL21. My biggest issue is it's lack of radius to fix turns, when the F1 GTN performs them flawlessly. The PL21 comes upon a fix with a heading change, and makes abrupt turns circa FS2002 style.
Bottom line, there's no suitable PL21 available for FS, that performs as good as the F1 GTN.
Being most of us don't actually have physical FMS keyboards, I see little difference in punching numbers on a GTN, compared to a PL21. The goal is the same, and the F1 GTN gets better results.