I viewed the same image in both apps and took screenshots of me looking at the same part of the panorama: Imgur link
. The quality is observably worse when viewing in Gear VR. The resolution seems much lower, and it's incredibly aliased.
I'm glad the 360 Photos team supports viewing photos taken from Cardboard Camera, but the degradation in quality is simply unacceptable. I hope this issue gets addressed soon.
S7 Exynos Nougat. 2017 Gear VR. Public test channel.