I started with leather.. Galco to be exact. But it wasn't long before I went head over heels for Kydex. Kydex can be thinner than leather and still retain its shape. Kydex can't degrade from the elements or sweat like leather.
Of course, Kydex isn't flexible like leather, which creates a minor design problem sometimes. Kydex also retains perspiration. It itches and it irritates when it comes in contact with my skin for too long.
I don't want to give anyone the wrong impression that leather is bad. Kydex is merely a preference for me.