Leave factory under coating alone or replace it ?

My first A body was a 65 dart that I used as a daily driver in western Massachusetts. I repaired salt related rust damage every spring and kept the car in black primer. The only parts that I NEVER had to touch....still had that factory undercoat intact (late 80s)
My current car has sections where someone attempted to remove it and gave up. It looks like a bear of a job and I suspect the modern, more environmentally sensitive replacement, is less effective. I'd leave it alone.
good luck