I have both stones, I have never really payed attention to the scratches the 12k Leaves as I finish on naturals.
I know that 12k gives a very nice shave and really with .5 diamond spray (what I prefer to CrO) give a really nice edge.
My current progression is up to 10k SS then natural, I do not use the 12k anymore because I do not see any benefit from it in this progression.