Not all leather is created equal! Quality costs but it also lasts. A purpose-built leather gun belt from a quality manufacturer will do the job very, very well.
I run both nylon and leather depending upon my attire for the day. Both are good to go all day long.
I will say that I prefer my Wilderness with the Kydex insert over my 5-Stitch but I usually carry OWB. I haven't ever noticed a big difference when IWB.
As far as marring the leather, anything can be damaged if abused. My Beltman gunbelt has seen over five years of regular use and it looks well worn but not beat up.
That's my $.02.