Here's one more for you, a short clip from last Saturday, the GoPro was just picking a mix of the on stage sound and what I had going through my monitor.
My personal experience is that they are ok for audio, but the Zoom's get you much better sound quality. I have the Zoom Q2 HD (you get video with it as wel)l, not as versatile as the GoPro video wise , it's a bit of a trade off. I think the Hero 4 is out now and have no idea if the sound quality is any better with that.
https://www.youtube.com/watch?v=NhpQMq9yccc&feature=youtu.be