They have improved the new Sony as you can use a standard camera mount without the need for the waterproof case, which is only needed for submerging the camera.I don't know what the Hero 3+ does with its low light mode but it is definitely closing the gap on the sony.
The only things the sony has bad going for it at the moment is the small fish eye that is noticeable and the lack of mounts (is that still a problem? ) the colour however is way better than any of the other cameras.
It will be interesting to see how the panasonic is going to do. Do people want to go back to the two piece camera? V.I.O isn't doing so well any more as these single piece cameras have become a lot better!
Panasonic seems to have made some basic errors, it has a non-replaceable battery, the camera is permanently fixed to the recording unit and the cable seems too short.
I personally think the Sony is currently the best but the Hero 4 with it's new sensor looks like it will be better, although rumours are Sony are going to fully utilise the 4K sensor soon.
I'm still waiting for Contour to release something that can compete, as it is still the best form factor.