I have seen some home building shows support the use of cast iron for suspended drain lines in lieu of pvc.

In the commercial market I understand cast iron is used however any thoughts on cast iron vs PVC for suspended drain lines in residential construction?

I thought PVC was one of the most durable products in the market

IMHO
The cast iron can make longer spans w/o support and OK in areas the chemicals in soil surrounds & water they carry don't destroy them slowly.
Aggieland's cast iron folly of old (soils, water demise) for lack of options, were converted & saved by the advent of the PCV era.

Use more PVC span supports, as per Mfr specs and don't look in the rear view mirror.
Also consider larger PVC diameters when apropos, ask me why.

I have no idea what he just said. But definitely use PVC in lieu of cast-iron. You will not outlive either one of them and PVC is a lot less expensive.