Nitron is a surface coating that is super hard on the HRC. Applied super hot. It is harder than melonite/tenifer.
Ferritic Nitrocarburizing is a metal treatment that penetrates the metal and increases the outside HRC and additionally reduces rusting. Tenifer, melonite, glock's older stuff.
Both muck up the metal. On the outside you have a super HRC. On the inside you softened the metal. More so with the Nitron.
The proprietary uses of "melonite" "tenifer" etc are the formulas. The process during the quench reduces the outer HRC to strength the mucked up inside.
Otherwise, super HRC on the side...boom. Brittle steel. Crack.
So it's not that the salt bath is stronger, it penetrates and physically changes the molecular structure of the top of the metal. Nitron is a top coating which is harder, but melonite/tenifer penetrate. You can knock of the super, super hard Nitron, but you can't physically knock of the salt bath metal treatment without actually removing metal (ex) from the slide.
Hard chrome is a plating. I've been extremely pleased with hard chrome. Least finish wear. But again, a salt bath is not a finish.