copper all day long mate
only a decent plumber would use copper (plastic fittings have rubber seals in them i.e hot cold, hot cold, they dont last forever im not saying theres ote wrong with plastic but ive ripped out copper thats 60/70 years old, and its as good as the day it went in

and i assume its roughly the same price as plastic

not saying your not a decent plumber turboboy just my opinion lol