mohair rope cinch!
Just be sure to clean it with a hard brush after use. If dirt/sweat/etc. builds up on the underside, it will rub them.
It's also good to stretch your horse's front legs out, forward, after tightening the cinch, to prevent pinching, but I do that with every girth!
I like a good rope cinch, because you generally don't have to tighten it as much as other types, since it stays put pretty well, plus it absorbs sweat and breathes really well. If you take care of it, your horse shouldn't get any galls or sores.
You can also wash them, by filling a small bucket with warm water and a little bit of detergent (either like wool-lite or one of the ones they make specifically for cleaning saddle pads and such), being careful not to get the metal buckles too wet. Swish around a bit, then lay flat to dry (don't hang or it will stretch) and oil/condition any leather pieces
The only real complaint with them, is that they can stretch, if you're not careful, and they require a little bit more cleaning maintenance than neoprene. But, imo, they're worth it :)