They have there purpose but don't fill the needs in my neck of the woods.
Lead sinks the quickest,gives the strongest signal it is on the bottom,is the cheapest and hangs up the most.I use it more because of the shorter runs in my haunts.

Slinkies are slower to sink.give a weaker signal that they are on the bottom,cost more,but hang up alittle less than lead.I use these on the west end where the drifts are bigger and can afford the slower sink time.