My reasons for going with the GoPro Black:
4k. No, I won't be using it for ANY video, but its effectively a 15 fps 12 megapixel camera. Will be great for pulling still images from.
120 FPS @ 720. I do most my filming at 720, and 120fps is twice what the ghost offers. Excellent for slo-mo.
Chest mount. Despite the rather unpopular square form factor on the gopro, it's the best for chest mount views, which imo, are the most accurate/real.
1080 @ 60fps. This allows for shooting a larger frame, so I can zoom in while post processing with no quality loss, it essentially gives you extra video real estate if you produce/edit in 720.
WiFi remote. I'm sure the Ghost has it too...
I've used the Hero 2 and have some mounts and accessories that will transfer to the black. Even if that weren't the case, I'd still go with the black.
**Extra batteries are always a great idea, no matter what camera you have