Braided stainless steel water supply hoses versus rubber hoses
The braided stainless steel flex supply lines are just jacketed with braided stainless. The jacket is there for appearance and perhaps resistance to incidental contact damage, but has nothing to do with the pressure rating.

In general, rubber hose is not used for faucets and cisterns; the hoses (whether jacketed with braided stainless or not) are commonly reinforced PVC (at least in my area, anyway). The washers are often EDPM rubber...