The chromium sputtered onto the edge is to make it slick -- chrome, platinum, and tungsten all, when coated, do not have the granular structure of stainless steel. The steel is rather "sticky" to hair as it cuts, so bare stainless blades drag more. Chrome and tungsten are definitely harder that the steel as well, leading to longer edge life. I don't know if platinum is harder, I don't think so. But they are all lower friction.
I find plain "super stainless" blades to drag more and be less comfortable than platinum blades, but the shaves are impossible to tell apart otherwise.
I find plain "super stainless" blades to drag more and be less comfortable than platinum blades, but the shaves are impossible to tell apart otherwise.