We had uncoated wire on our cat when we got it. The first time I slipped and my shin slide against the uncoated wire it neatly sliced off a peal of skin. There is a reason they make cheese slicers with uncoated wire. Yes, the lifeline is thicker, but naked wire can cut and vinyl is much more foregiving. Particularly with kids on board, we decided it was worth it to coat the naked wire with vinyl.

Yes, rust can eventually accumulate. But if you rinse it off once in a while it takes years to rot and you see the discoloration at the termination, and it's not that expensive to replace.