What is a CFP?
In essence, a high gain super transistor, somewhat similar to a Darlington. But there are major differences. Unlike Darlingtons, there is some voltage gain with CFP. Another unique feature is local feedback, so there is an "hide gain" inside gain one outside.
Why is it not as popular as EF?
Basically, more difficult to design then EF. When local feedback is nested in a global feedback, an amplifier is more prone to instability. In other words, it is easier to break out into high frequency oscillations. But a well designed CFP Output Stage can often be outstanding.
This is where it probably makes a real difference. With listening tests, the Sziklai Outputs are the most enjoyable of the three designs. It sounds faster and the highs are smoother. This is probably due to a wider bandwidth and faster rise time. All these are achieved without compromising bass slam and definition.
Wilson current mirror instead driver resistor load can solve instability problems because try to equalize the currents
reducing the gain hidden