For me, the nylon is more comfortable to wear, holds more inside the sheath than the leather sheath, and the quality is good.
Some other well known brand multi-tool nylon sheaths start falling apart in a couple months. I figure when the velcro wears out; I might have a metal snap put on it.

The leather sheath leaves much to be desired. It is too small to carry both the tool AND the plastic bit holder. The nylon sheath is the way to go!