Quote - thats because of the specular.  the diffuse is the same.

Respectfully, I have to disagree. Even the shadows in the two images are different.

But in any case, think about the two different processes you are using to reach a final image. Each separate pass renders with GC, then you combine these GC'd images in Photoshop. That's not the same as combining in linear colour space and applying GC to the end result.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)