I put mine on the POS cable. My NEG is a braided strap. My logic was if you put it on the NEG side then anything metal falling across the battery posts will create a circuit. On the POS side it can't. My 2 cents.
Another neat rumour about cut-off switches is that you have to polarize your regulator each time you disconnect the battery. The electrical shop in town insists it be done but others say not. I have had it in for 2 years and never polarized my regulator.
