My post from the A&CC forum post:
Which is interesting because on EFIS , there a huge difference between models and even within the same model over the years. , some previously controlled by side buttons now touch screens and tens of new functions added , of which over half you will never use .
This is my concern. I think back to the late days of LORAN C, and transition to early days of GPS, I was ferrying all kinds of complex singles for an English company. Each airplane had a different navigation system, and the only functions which were universal were On/Off, and the "Direct" button. Otherwise, they were all different, and required a good read of the flight manual supplement, and erasing what you just learned about the other system. And, that was only nav, for VFR flying. Now, we have very much more complex and integrated systems, which include autopilot, and more to the point, may interfere with the pilot control of the airplane in the background (Garmin ESP). And, more, more to the point, these systems are being retrofitted into legacy types, which may already have other modifications which the avionics installer has not considered as a possible source of system conflict.
There is an exponential burden on pilots and owners to understand these systems, and their integration in the airplane. In my opinion, "instructors" in the GA/PPL world are more commonly primary skills instructors, and their in depth experience with advanced avionics may be incomplete. So, getting a "Instructor checkout" in a complex type with advanced avionics could be incomplete - and the PPL owner does not know what they do not know.
This situation, with very advanced avionics in GA types is diverging from "good" in presenting pilots with task intense operation, competent training is hard to assure, and the airplane is more capable of taking the pilot into more demanding conditions - with artificial confidence.