Different plants across the nation have different results.
I can only speak for the plant that serves me here in North florida.
The moire black is a lighter shingle.
It has no variation at all and is a disgrace to this once great color that was/ is Moire black.
The Charcoal is a little darker and it does have some variation.
The Charcoal is the one that i choose now
Because i can see its variation.
"Light and dark colors blend for a natural look"
Used to be written on every certainteed sample board.
My particular certainteed plant has FAILED
With "moire black"
Other plants might still succeed in the moire black with some variation in it but i can not speak for it.
As someone else said,
The charcoals fade every year that goes by,
So dont worry at all about one being too dark.