I prefer adjustable sights. Not for adjustability but for a superior sight picture.
There is color case hardening and there is case hardening. Parts can be case hardened without colors or they can be intentionally case hardened in such a way that colors are imparted onto the part. Both are hardened.
The Ruger finish is neither but a chemically applied case coloring intended to imitate the real thing. They tend to be more rust prone than white steel and that is why it is no longer offered.