We get asked this quite a bit, and it’s a good question. You would figure with the hard plastic that kydex is made out of that it would cause more damage to the finish of the firearm in comparison to a soft material like leather or nylon. The trick to all of this is to look at what causes the wear in the first place.
Wear is caused by abrasion, and abrasion is caused by having roughness to a surface rubbing against another. The surprising thing here, is that kydex is actually smooth, even more so it doesn’t have pores to capture dirt and dust in! So that leaves it all up to the holster maker to do a good job of keeping the holster sleek and smooth drawing to keep wear to a minimum.
Leather and Nylon holsters are full of small pores and have a fine texture which causes them to act like fine sandpaper. Over a few dozen draws on those materials you can start to see the wear and tear showing up. After a few years you can only imagine how bad it will get. Combine that with knowing that you can’t wash out a leather holster, and you can only wash a nylon holster so much before it starts to come apart, and a Kydex holster pays for itself quickly.
Long story short, because of the smooth non-porous material that kydex is, it actually makes for less wear and longer service life of the holster.