Can anyone describe the differences in the various GTN STC installations for CJ's with Proline 21 panels? Jet Tech vs Textron? Other?

What works, what doesn't? Functionally intuitive, or is it a head scratcher? I'm pondering a CJ2 and would like to understand the avionics options.

Go with Jettech over Cessna for the STC. Don’t remember the exact difference but Jettech will fill you in. Commonly 2 750’s or 1 750 and 1 650. Most seem to pull the Universal.

Jet tech.

I was told The Textron STC doesnt allow Garmin software updates.

The Jet tech STC is much less around 15k.

Lol,
what is Textron drinking. Once its in the plane and the software is available from Garmin...

That is correct. Textron CJ2 GTN STC specifies a specific software version number. In addition I hear it is glitchy in coupling in some vertical approach modes.

Advantage of the Textron STC is it updates the PL21 PFD SW so RNAV approaches are displayed in the same magenta symbology as the 1+/2+/3 has. ILS/GS shows as green; RNAV shows as magenta. The added cost for the Textron STC is due to the PL21 updates.

I believe on the Jettech STC both ISL/GS and RNAV show as green on PFD.

Also with one of the STC's you must remove your UNS1 and the other you can retain it. Without the UNS1 you lose some fuel planning abilities. The GTN cannot sense and synch fuel onbaord the way the UNS does.