fd178d24_n_and_How_Should_They_Be_Used___Strengths
[Line] Plastic coated multi-strand wire (1x7) [Weaknesses] More visible than mono or wire, coating susceptible to teeth or abrasive surfaces, undetected corrosion inside coating. [Strengths] 
Inexpensive, resistant to sharp teeth, more supple than single strand wire, easy to handle, easily joined with crimps, small diameter
Fishing Leaders - Just Why, When and How Should They Be Used?
Strengths