Walther uses the Tenifer QPQ treatment on their carbon steel slides & barrels.
My SW99 stainless steel slides, which have received the Melonite QP treatment, have proven to be very durable as far as holster wear/scratch resistance is concerned.
Ordinary bluing is generally considered to be right down there at the bottom of the scale, or right close to it, when it comes to "wear resistance" and corrosion resistance issues.
There are a lot of different proprietary finishes being offered nowadays, too, and some may offer better wear & corrosion resistance than some others. Buyer beware ...
Some folks who carry 'blued' finish SIGARMS in another agency have reportedly complained that some of them would start to oxidize by the end of their 8-hour Patrol shifts in certain weather conditions.
I remember a lot of our senior guys carrying issued blued Colt Pythons when I was new, and watching some of them methodically wipe down their revolvers at the end of each shift, and take special care if they had been exposed to rain/moisture. Of course, a lot of those older leather holsters covered more of the revolvers than many of the duty holsters used with some pistols nowadays, and maybe that had something to do with the revolvers being somewhat less exposed to the elements over short periods. Dunno ...
I think nitrocarburizing treatments offer some distinct advantages over some other 'finishes', but I also think they still require some reasonable owner/user care and maintenance for optimal service life.
Just my thoughts ...