Finally read through most of this. Phew! I'm just going to throw this out there from an engineering perspective relative to my background, education, and experience with two silencer companies.
Product performance requirements should dictate your design and material selection. Of the materials listed, Stellite, Inconel, 6Al-4V, and 17-4, all offer pretty insane material properties on the face of them so most manufacturers can get a way with using them how they want. Several companies are using materials based more on what their manufacturing capability/supplier base is centered on. Any given material stat like tensile strength, density, etc., shouldn't solely drive the decision for its selection in a product. It's a combination of all of them for any given product performance requirement.
If you want the most durable baffle possible, you can't focus only on material. It's MATERIAL plus GEOMETRY. This is a common error in the industry and it's entertained me for years. If you take a sharp-edged Inconel cone (say like an M4-2000) it will wear away the edge around the bore like a steep, sharp, knife blade will lose its cutting edge faster than a blunt, sharp, blade will. A little extra material, a flat face, maybe a 90 degree shoulder, and 17-4 baffle will withstand a test that will hollow out that M4-2000 with those sharp Inconel cones. Even a little bit of wear on that type of geometry means the bore hole enlarges itself. The method of failure along the bore is quite literally a ripping away of the granular structure of the metal. Stellite has the most durable of the crystal grain structures. All the way on the other end of the spectrum, 6Al-4V (grade 5 ti) has a larger crystal grain structure and when it wears, it's bigger chunks that fall off.
Add it all up, and on one end you'd have a baffle made of Stellite (superior wear resistance because of its granular structure) with a durable geometry that withstand incredible heat and abuse. On the other you have 6Al-4V Ti with a knife blade sharp geometry that's going to wear more over time and hit a point where things fall off precipitously.
Baffle strength aside, there's still the whole structure of the suppressor. Most manufacturers that are falling back on the materials listed are going to do great as long as they're spec'ing enough material and strong enough joints (I'll call this good Design) and also manufacturing well (I'll call this good Process Control). Many focus on one, but not the other. It's difficult to do both without a lot of talented people on your team.
For us at Dead Air, the decision to use Stellite was not one for saving weight, or money, or manufacturing costs. For the Sandman product line, it was solely about durability. If you add up the material and geometries used in the baffle, no other material will handle the abuse it will. Just as importantly, there are product requirements like great sound reduction, tone, low weight, and the ability to easily be removed from the host weapon when all is said and done. I personally feel that our Sandman -S would the closest thing to a "belt fed" can among the mainstream products out there because of the baffle and construction design as well as the attachment method. Otherwise, the obvious choice is AAC's MG-SD because it's made of a good material with uber-thick walls to account for the wear that will occur.