i prefer quality knapped flints over cut flints.
if a flint sparks well, it's a well flint.
a well flint is a good flint, no matter where it came from or what is its color.
i think entirely too much is spent on flint debates.
all that matters are the sparks - and if a flint isn't sparking well, it might need knapping, or it's improperly positioned and angled, or it's striking the hammer steel incorrectly, or it could be a hammer steel hardness issue.
however, i prefer "fine" flints - that is, a thin flint with one cutting edge, not a "common" flint with a high middle peak and dual cutting edges. i could care less if it's black or amber. fine flints sit better in the cock jaws, for me, and only one edge is needed, which will get knapped to be kept sharp.