I still like good old mohair. Or the new alpaca cinches.
As for the latigos and off billets, I used to like nylon because it would slide over itself and tighten easier. But a neighbor got me into using leather, and you know, I use leather on both of my saddles now! I got used to the extra "stick" when it slides over itself (and to make it less sticky, avoid saddle soap on your latigo). Now I think nylon looks kind of cheap.