The darker looking ones have AA (High, SMAA), SSAO (high, high-quality scale, sharp), DoF (bokeh), Bloom, Posprocessing (durante)
Postprocessing settings are a bit tweaked by me (bold):
The "lighter" screens are with all above mentioned toggled off.
Here two more "comparison" gifs between "vanilla" and fully pimped out GeDoSaTo Dark Souls II (1080p, same settings as written above).
I took special care to take screenshots at exact same lightning, so that all differences are much more correct. Difference is crazy, a lot more than many lastgen to newgen ports I dare say.
Another neat effect is that the visual differences are more than just eye candy. The much better and atmospheric darkness changes the way to play even!