The advantages of the Blurfix are that the lenses are glass (vs plastic) and they are interchangeable (they'll fit any 55mm lens from a photography store). This is a great advantage when you scratch a lens and it needs replacement. The GoPro housing is cool, but I like the flexibility of being able to remove the adapter and find parts without special order. Hope that helps.
One of the raddest free-diving videos I've seen, damn inspirational. Nicely done!