In reply to nicboarder: As far as I know, katanas used to use XS grip, now they're on the supposedly harder wearing, cheaper, and not-as-sticky XS edge.
The stiffer compound in edge crumbles or shears off more perhaps? I nearly bought a pair of almost-new katanas on here to replace my old ones. Toes were worn to the rand after 'worn them a few times' so I didn't. My XS grip katanas did ~18 months of probably ~10 hours training a week and didn't look much worse at the toe.