The PEX lines are actually cheaper, considering the labour costs of installation.

The comparitive amount of time to line up straight sections of copper pipe by an installer to get a straight run can take a long time. If you look at some new construction, you will see that the installers make "modifications" to the holes to provide that straight run of copper pipe. Sometimes the holes made interfere with load transfer, causing a failure of the plumbing inspection, and calling back a framer to fix the problem before finalization. BC building code requires that a pipe be bent in certain ways to relieve the expansion/contraction of the metal, especially crawl-spaces or unheated areas. See the Alaska Pipeline for examples of expansion joints. All this requires time to dry-fit and solder, causing more time.

PEX can be fed through ane hole, pretty much anywhere in the plate/sill/wall/joist/truss as long as a special mending plate is used to prevent someone accidentally putting a nail or screw through the PEX. The crimps are bent on with about 1500psi with a special hand crimper, and I've heard that PEX shrinks about 5% in the first year of it's manufacture date, so I doubt it will ever leak after one year. I sold PEX for almost ten years, and never heard a problem.

Some of the guys will swear by copper pipe, some will swear at it.

almo