There was another thread elsewhere on this, I mirror'd HA's comments. Poly leaders are just more versatile for the bulk of the PA troutin'.
That said, on sinking lines, there's intermediate and then sink types 2 through 4 (or 5?). Intermediate sinks very slowly, the sinking types progress significantly in the speed in whcih they go down, and the amount they weigh.
There's also the way people make their own heads for spey casting, etc. Usually they cut back pieces of lead core line to specific weights. Its complicated, I don't profess to care.
For simplicity sake, buy a type 4 poly leader.