If you want black, go with nitriding.
If you want stainless looking, go with hard chrome by Mahovsky Metalife
I sent a rifle off for Black T. It's been decently durable over the years but does have scratches thanks to alpine hunting for deer and goats. I think of it as a tougher version of ceracoat since it's still a coating. The above two are the toughest things I know
What he said!