I am also struggling to decide on what to buy after shooting with the P2H4 combo.. I think the smart thing to do is just wait... I'm still getting great footage with it. it's just a complete pain in the **** to do post work from it's footage because its all big 4gig chunks that needs 70% of the transitional fat cut out. If I had the ability to start and stop and lock the exposure on the Hero4 I wouldn't even consider spending the money on anything new now.
Considering optical distortion on the cameras.....
I'm not completely convinced that the P3 is using the same lens as the inspire.. The slight barrel distortion on the inspire is nice and clean and consistent from edge to edge and the P3's isn't.. The Gopros all have the same exact barrel distortion regardless of FOV, because your not changing the optics when you switch FOV, your just doing a sensor crop, so you are still seeing the same distortion, your just not seeing the edges of the sensor, which has the greatest barrel distortion when compared to the center. But the Hero4 Barrel Distortion is clean and consistent across the entire frame.. Much easier to work with in post. Plus, I personally use the fisheye for some situations... So yes, the Distortion is still there in MED FOV on the GP, it's just not as apparent.
Sometimes when I boot up the P2, I end up with a tilted horizon. I fix this by just rebooting the gimbal. If it's straight before takeoff, it stays straight throughout the flight.
No issues with the P3 gimble not being level, but we only did a few quick flights and ground tests to specifically compare the image quality on the cameras on a chip chart.
For me, all the fluff and added features that the P3 adds is cool... But to be honest, I care mostly about raw footage quality..