People is it me or do plastic holsters scratch your gun a lot more than a leather thats been oiled? I say no to plastic because I personally seen it scratch guns...
I HATE Fobus. That being said not all plastic holsters are bad. Blackhawk Serpa CQC holsters are awesome. I have one that I used in my Glock 17, 19, 26, 22, 23, 27, and 30. Virtually zero wear on the weapons. I placed my BRAND NEW Glock 23 Gen 4 in a Fobus holster ONCE and there's a nice big permanent scuff mark now. The Fobus is specifically for compact Glocks.
I actually got more wear on my Glock slide in the 6 months i carried it in a leather Galco N3 holster than I have gotten on it carrying it in Kydex and plastic holsters in a combined time of over 3 years.
Its the environment the gun is worn in more than the holster material. I had a leather golster that trapped everything against the gun and scratched it pretty bad. I switched to a Fobus because it kept the gun high enough to hide under my shirt at work. My gun still wears but I work outside construction and with dogs day in and day out. I have to clean it every week because it gets so disgusting. I have a friend with the exact same Kimber and his will rust if he's not careful because he sweats so much. He uses a Crossbreed.
I find that both can scratch the gun, but if you're holstering it, it shuld be something you don't care that much about. Leather has more of a tendency to trap dirt and then rub it against a gun, and the inside isn't that easy to clean. Plastic is, well, hard plastic and if it's not made to sit off the gun and only retain it at the trigger guard, it will rub the slide. It's much easier to clean out if the inside gets dirty though.
There is not a holster made that won't scratch or in some way wear the surface of the gun. I have a "pocket gun" it is always in my pocket with nothing else in it, the checkering on the grips is almost smooth now and the stainless has changed color. The oil in leather will hold dirt which will start wearing on the gun surface. You can not stop normal wear unless you keep the gun in a sealed container and don't carry it.