An update to the original Digital Foundry article by "Brian Karis, senior graphics programmer at Epic Games" seems to explain most differences:
"Feature wise most everything is the same, AA resolution, meshes, textures (PS4 has tons of memory), DOF (I assure you both use the same Bokeh DOF, not sure why that one shot has different focal range), motion blur.
"Biggest differences are SVOGI has been replaced with a more efficient GI solution, a slight scale down in the number of particles for some FX, and tessellation is broken on ps4 in the current build which the lava used for displacement. We will fix the tessellation in the future."