[fencepost]

It's interesting but not surprising that this competition exists. I'm not sure the concern about what leaches from the plastic pipe is legitimate, since it seems like a lot of ductile iron (which replaced cast iron) is also plastic lined though with a different plastic. Iron may have a structural strength advantage, but how important is that most of the time? Finally, plastic pipe may have the advantage in some locations due to the nature of the soil - there are some places where the soil is more likely to cause corrosion in the iron, and for those it seems reasonable to use plastic rather than simply coating the iron in it.

Overall I think the big advantage is going to come from actually getting the aged pipes replace more than from the choice of which new material to use.