Pin Hole Leaks!

What is the cause or causes?

Replacing (m) with (L)...a real fix or a thicker band-aid?

Who wins the "install me!" race right now...(m),(L) Copper, CPVC, Pex, or other?

You have to find out the core problem of the pinhole problem, otherwise you are covering up a problem without curing it.

The copper tubes serving the feed lines to the faucets along with the internals of certain faucets have copper in them.

Replacing M with L is fixing a symptom, not the problem.