Who's PBR node setups do you think are most accurate?

There are a ton of setups for PBR Metalness workflow and PBR Specular workflow. I like both but I want some of this stuff to translate to the Unreal engine (metalness) and some to translate well to other renderers like Redshift or Vray (specular).

There are a lot of people claiming they have great PBR shaders but they always tweak the math or do something different and it’s hard for me to discern who is doing things the most correct.

So, who’s do you think is the best for both Metalness workflow and who’s do you think is best for specular workflow?

Bartek Scorupa (jump to 25:49, or watch the whole video because it’s Bartek Scorupa) :

The point is, the best is not the most accurate, as it’s a pain to customize and it’s not worth it for the tiny difference it makes.

To me Cynicat pro’s are good enough.

About translating to other engines, why not directly make the material in the engine itself and find a tutorial or downloadable node setup for this specific engine ? I don’t get the point of making the material first in Blender and then in another program.