I have the Hero4 Black and also the blackview dv800b. hero4 is 500$ and an awesome action cam, but I am protective of it. The blackvie dv800b was 100$ and although the quality is less, I am not afraid to use it in very extreme conditions. Both are great little action cams. I use both at the same time when I am filming some outdoor activities. To compare the both, I am not going to do that. Hero4 would win, but I needed 2 action cams, and did not want to spend much for my "B" camera. I have been pretty happy with both of them. Here is the review of the blackview dv800b.
MAKe SURE you DON'T BUY a FAKE COPY, do you homework.
I am looking forward for the
BlackviewDV800B.