I can’t really tell the difference between 10k and 12k unsurprisingly
For me, the difference is that I know that after 12K with very light slurry (or just plain water) I can go directly to stropping on linen and leather. With 10K, I feel as if I want to take some passes on a loaded strop before moving on. I honestly doubt this is necessary, though. I think a Puma 89 comparison (I have two Puma 89s) between 10K and 12K Advance (Superstone) should get on the “to do” list.
For me, the difference is that I know that after 12K with very light slurry (or just plain water) I can go directly to stropping on linen and leather. With 10K, I feel as if I want to take some passes on a loaded strop before moving on. I honestly doubt this is necessary, though. I think a Puma 89 comparison (I have two Puma 89s) between 10K and 12K Advance (Superstone) should get on the “to do” list.