The black looks much too harsh/severe. My own choice would be a gray similar to this.

neither. I would choose Granite Gray.

the black is way too harsh and the Pewter looks too blue/purple.

Thanks for the feedback. I am worried about the Pewter being too blue, however Granite gray isn't available in my part of NC. Two other options that are available in landmark pro are Colonial Slate and Georgetown Gray.

Have the roofer pickup a bundle of the two choices and actually lay them out on your roof. Do not pick from a sample board or a computer rendering. My vote would be Granite Gray or as close to that as possible.