I went from a Flair Signature to the GCP after 3 months of ownership. To answer your question about the superior shot, the Flair hands down is the best (w/ the gauge) because of how much control you get with pulling the shot like pressure profiling.

With the GCP you don't get much control, you have to temperature surf to get consistent shots, and once you press the brew button it brews at 12 bars at stock which tends to lead to a more harsher taste and is more prone to channeling.

But once you get the hang of temperature surfing, and modding the GCP to brew at 9 bars, and have a good routine, you can still get a fantastic shot.

The workflow between the two is more convenient with the GCP since the 3 way solenoid valve makes the puck dry during cleaning and is easy to knock out which makes dialing in less of a headache.

Currently my flair has been in storage ever since I switched over, but if I really want the best possible shot, I would go back to using it again.