We have gotten two quotes to replace our old galvanized water supply line (pipe from the water main to our house). One plumber uses PEX and the other uses black polyethylene. I know both options are cheaper than copper and both seem to be good options, but I don't know if PEX is better than black poly/PE. The PEX quote is a bit higher, and I wondered if it was because of the type of pipe. Is PEX better than black polyethylene?