A nylon holster without a lining will wear finishes faster than a fitted leather holster. This is not only because the nylon holsters have a "generic" fit (i.e., made for guns of the same general size but not molded to the contours of your gun), but also because the material is more abrasive. One of the few exceptions to this is the Bianchi "Accumold" line, but they are made for relatively few handguns and are more suitable for open/police duty than concealed carry. Even those with a lining (what some wag here called "cloth-and-sponge pouches) suffer from a loose fit.
If you handle, carry, shoot and practice holster draws enough with any handgun, your finish will get worn, to some degree. It is unrealistic to think it will stay in pristine condition forever.