david weaver
I have pictures of a 13k sigma somewhere compared to the formax edge. It's interesting to look at them, but they're probably almost identical aside from a softer backing for the formax compound will make for a cleaner edge with no remnants.

The pure chrome powders leave a surface finish that looks visually perfect, as long as the backer is clean (as mentioned in a post above, my only use for them is setting up a razor for someone before I unload one - there's a large segment of the market of buyers who will open a razor and look for anything they can see naked eye and possibly with a loupe, and the chrome ox powder (0.5 or less) leaves absolutely nothing to be seen).