Personally I would rather have copper which is a natural metal our body needs (small amounts), then plastic because we are already exposed to so much mircoplastic. Copper does get pin holes over time which is why everyone switched to pex, and of course pex is cheaper. But you are correct it does depend on the water chemistry, different areas have different water, so it really depends. I've never plumbed using stainless although I have done service work where stainless was previously installed, so I'm not really too sure about that.

Based