As far as honing and the final edge, no difference. But being a natural stone, there is variance between stones.

Select and standard grade is based on looks. A select grade coticule will be free of "blemishes" or in clusions. I have not come across any inclusions that ever affect the edge.

I like Ardennes quite a bit. I have purchased 2 from them directly and 1 indirectly. All give fine edges, as do most of my vintages. Although the edge is a bit better with my modern ones, I specifically state in the comments/howw will yoiu use the stone; "stone will be used as a finishing stone for straight razors." How much of a difference that makes, I'm not too sure.