Many plumbers prefer PVC over copper and vice versa. Despite your opinion between the two you can display to the interviewer that you are knowledgable in this area of plumbing work.
"I feel that there are a few advantages to using PVC for water mains. For one, it is resistant to corrosion and abrasion. Secondly, it is less noisy. Thirdly, it is more cost effective than copper."