Dear Mr. Martin,

As probably you will know, the diameter of the dimple (impact) is directly dependant of the intensity and the diameter of the media. And the depth of the compressed layer for a sigle impact is three times (aprox.) the diameter of the dimple.
So, in your example, i would suggest you to expect similar depths for both media.

Eduardo Vázquez
IPAR-BLAST, S.L.
(943)820516