Thanks for posting results of VRS range plot.
Comparing the range plot of pcb with 1/4 w gp, both are almost identical.
This is with both the antennas indoor. It will be interesting to see how the two antennas compare when both installed outdoor.
An interesting comparison which proves antenna theory is alive and well <grin>.
I'd expect the PCB antenna and a 1/4 wave ground plane to have the same performance because one is a variation of the other. The PCB antenna is a centre-fed 1/2 wavelength dipole (with the method of feeding it resembling a flattened form of coaxial dipole), which has the same radiation pattern and gain as the ground plane. The PCB antenna certainly lends itself well to being mounted in a radome for weather-proofing, resulting in a cheap, low profile and low weight antenna.
FWIW, some PVC pipe is not transparent to RF, and can be very lossy. A quick test is to place a short length of the pipe in a microwave oven, along with glass of water, and run the oven for 30-60 seconds. If the PVC stays cool it's a satisfactory material for the radome. If it gets warm or hot, don't use it with the antenna because it's lossy and absorbs microwave energy (including ADS-B).