Well, the Hero4 Black, P3A/P, P4, and Inspire 1 (X3) all have the same Sony sensor. They all have the same f2.8 aperture. The P3P and P4 will likely be better overall, since they can record 4K video without the fisheye effect. HOWEVER: the Hero 3 Black also has the same f2.8 aperture, so overall the low-light performance of all of them will likely be very similar, though the P4 and Hero4 may be marginally better since they are newer versions than the H3 black.