What is the difference in ware to a pistol's finish carried in kydex vs leather holster?
Anything you carry a gun in frequently will show "wear" on it eventually. With that said, the guns that I carry in Kydex do seem to have more wear marks on them and faster than the guns that I've only carried in leather (talking guns with similar finishes ).
Kydex will wear a gun's finish faster than leather; but leather must be kept clean or it will accumulate grit which can scratch a gun's finish just as quickly as kydex.
A lot depends on how they're fitted. A good kydex rig that only has a minimum of friction points will wear very little, whereas a leather holster with a lot of boned fitting will wear on the finish rather quickly.
As noted, keeping them both free of debris will go along way to minimizing wear and tear on the finish. That's a very easy thing to do with kydex.
My experience is Kydex is more inclined to wear at specific points on the firearm, whereas leather wears more evenly over the entire gun. I have seen wear lines (where the lip of the holster rubs on the slide) develop in a matter of a day or two of use. Typically the rest of the slide has no wear.
Drawing a blued pistol just a couple of hundrerd times from a kydex holster will produce significant wear. That has not been my experience witha good leather hoslster on a similarly finished pistol.
Easy to get this kind of wear in just a few days of concentrated training.
I wore the finish off of a couple Glock 19’s carrying them in Kydex. No big deal, the gun was meant to use and they make a million of them every year.
I carry my FNC Hi power in Leather and it wears a bit too, but it’s easy enough to be refinished if it bothered me, which it doesn’t. Go with either and use your gun. Refinishing is cheap if it becomes necessary .