I did a quick and dirty side by side video comparison of my GoPro Hero 4 black and the Phantom 3 Professional. I used a gopro on a pole underneath a hovering quadcopter for the footage. Both set to 3840x2160/30p. There are massive exposure and white balance differences between the two which makes quality comparisons hard. It's just a side by side test with both cameras set to auto exposure and auto white balance.
At the end I did some level adjustments to try and put them on the same brightness/contrast level.
The GoPro hero4 has a much wider lens but it does distort at the edges a lot.
Here is the test video shot at 4k with both camcorders at the same time -
lvl.3
