I use these on quadcopters too.
The GoPro firmware seems to do better at setting exposure. Light-to-dark and vice-versa is hard for the Mobius. It adjusts the shutter speed and ISO/sensor gain together (like most digital video cameras do) to set exposure, but it seems to do it with noticeable notches/steps, and not as quickly as the GoPro does.
There are a huge wealth of customizations and firmware options for the Mobius thanks to the community, but that also means you have to spend time tweaking to get the best image.
For the price difference I think the Mobius is a better camera, but for those without time/energy to tweak or for situations involving lots of lighting transitions the GoPro is still better.
My biggest problem with the Mobius is actually that it's so small and light (and the form factor is so strange) that it seems to be more prone to vibration than the GoPros.