Linen (the fabric, not necessarily “bed linen”) is better, it absorbs the blood differently and leaves a cleaner surface for longer, but I am told that linen is pretty rare in the US, and cotton more common. You can put a leather or a synthetic core in to prevent soakthrough. Leather isn’t machine washable (less of an issue in a post apoc world, but I live in a pre-apoc world) so synthetic layer is better. They smell less and work well, and cost little. I recommend to all.