Two 8-bay antennas will have a larger capture area, but that doesn't guarantee signal increase, as I mentioned in post #9. The larger capture area theory assumes that the wave front is uniform across the whole antenna; that is rarely true especially with weak 2Edge signals that have been scattered by terrain interference.
The DB8e has been optimized for the latest 14-51 band. I have no idea about the actual gain of the HDB8X based on range tests.
In this case, a smaller capture gives a stronger signal:
