I have both. I use the Sorbothane for anti-vibration mounts when mounting GoPros on race cars. The MoonGel appears to be a softer durometer (30) versus the Sorbothane sheet material (50). I found the MoonGel at a musical instrument store in the drums department. The Sorbothane sheet was purchased on Amazon.
The drawback to the MoonGel/Sorbothane option when put between the GoPro mount and the fuselage is that vibration is still being transmitted through the mounting screws. If you look at commercially anti-vibe mounts the camera is completely isolated from the fuselage with rubber dampers.
I have had really good luck by carefully balancing the props and setting the camera at 720 resolution at 60 frames per second.