I hate neoprene cinches. My friend's horses always stink so bad with the sweat dripping out from under the neoprene. And one horse (a friends, not mine) used to gall really bad with neoprene. So I have never had the urge to buy one.
I like mohair (or alpaca) myself. Soft, strong, breathable, natural fibers.
To clean periodically wash it out in a bucket of water right after you take it off the horse. It will rinse easily and then hang to dry. No problem with dirty smelly cinches.