The factory kydex is good. I've had them as well as the leather. I prefer Armatus' kydex sheath, however. Comes with a great pull-the-dot strap that holds it close to your body, almost like Bob Dozier's horizontal kydex, and still lets you attach/remove it w/o removing your belt.
I'm wearing one right now with my G3 and it's almost as comfortable and invisible as Brad's leather sheaths are.