Either one is ok to work with if you know how. Cast irn is heavy need cutter to cut it are sawsall and torck wrench for bands. Pvc is light, need saw gloves glue cleaner, eye protection. Better just have Plumber do it because when taking out old iron the stack has to be supported.
Have a plumber instal cat iron. If cabling is ever needed from the roof, the cast iron wil stand up to the abuse. ever see what happens to a pvc stack when a sewar machine is left on while the plumber goes done to sound out a line? hmmmm….spining metal cable inside of a bone-dry pvc pipe……….no water to cool the heat created by the friction…….pvc turns into a wet noodle……….cable cuts a line right down the tip off the stack to the shingles. I like cast iron.