As an avid user of the iPhone’s camera, I can say that this app takes better nighttime photos. Cortex cam even takes better photos than the iPhone6 in some normal-lighting situations.
Caveats: If you are not used to taking pro photos, you may not notice the improvements. I don’t always walk around with a DSLR, but still want to get the best I can when i only have the iPhone. iPhone6 made huge leaps, but zoomed low-light shots are still wonky. Cortex gives you that back (as best you can have it on an iPhone) — though when you are low-light + zoom + extreme brightness mixed with [architectural] details (like lots of neon on a sculpture) then you will get minor washout of the colors. Except this situation, the the photos will be better than iPhone6.
Caveats: you need to mount the shot, or use some kind of bracing. A long exposure time is used to gather enough information to improve the image. If you hand-shoot, you’ll limit the range of shots that you can meaningfully make. Naturally, if your target is in low-light and moving or changing colors, you may not be as pleased with the shot compared with a faster shot that is more grainy.
In normal lighting shots, I found that only the smallest of details were resolved better, and when saving in PNG mode. E.G. the lettering on distant signs was garbled on iPhone6, but clear with Cortex cam. Most general information does not appear to be improved, so the casual shooter will not see value. I also found that I had better color rendering in the medium-light shots, especially with reflections.