As I am looking at my next plane, I realize I don't know much about autopilots.
Which autopilot is better than who, which has what functions/limitations.
Has anyone ever compared them and made a chart.
Especially:
KAP140, GFC 700, GFC 500, STEC 55x, TRIO, TruTrak, original Cessna AP's
Trio and TruTrack are not certified for IFR approaches, so if that's important to you, that washes them out.
Most older autopilots like the Century depend on the attitude indicator, so if you have a vacuum failure, you lose your autopilot at the same time, when you would otherwise have needed it most.
Second-gen A/Ps from a couple of decades ago, like the KAP 140 and the older S-TECs (e.g. the S-TEC 55x or my S-TEC 20) are rate-based. That makes them independent of the vacuum system, but they're
slightly more sluggish in response than attitude-based A/Ps. They were the best option before AHRS for safety of flight. They're good enough for approaches, but you'll weave a tiny bit in strong or gusty winds, and sometimes overshoot a turn slightly.
Modern third-generation A/Ps like the GFC 500, TruTrak/Aerocruze 100, Trio, S-TEC 3100, and Aerocruze 230 are digital AHRS-based. They're independent of the vacuum system, like the second-gen rate-based A/Ps, but have the faster responsiveness of the attitude-based A/Ps, so they're the best of both worlds (in a sense). If you're VFR only, the TruTrak/AeroCruze 100 or Trio will be the best deals. If you're IFR, you'll probably want an A/P that can legally fly coupled approaches, so the GFC 500 is the most-affordable option (if it's available for your plane).