We repiped our house last month with L-class copper to replace the thinner-walled M-class copper used when the house was built ca. 1987. We were offered PEX (plastic) at 25% lower total job cost but declined.
PEX comes in 2 flavors, A and B. The bidder pushing PEX-A said in a dire tone, whatever you do, don't use PEX-B!! You'll never guess what the bidder pushing PEX-B said.