Given that this was only a mic test between the Action 2 and Hero 11 and I didn't optimise any settings for video. I'm really surprised by how well the Action stood up against the Hero for the video.
In fact, I feel that I made a bit of a tool of myself with that comment about which one would be better for video
Maybe I should send the Hero 11 back to GoPro with a complaint that it isn't that much better than DJI's effort from last year
Picture quality aside. The Action 2 clearly has a better microphone compared to the Hero 11. The Action 2's mic reproduces a better, wider, frequency response and dynamic range. The Hero 11 unfortunately suffers the same curse as all GoPro cameras, too much gain on the AGC which is severely limiting the dynamic range when it is slammed into the dynamics processing after the AGC. Plus, the GoPro frequency response is just a bit too limited, which when coupled with the restricted dynamic range from the AGC, just results in a very restricted overall response compared to the Action 2.