We had a deadly combination of low pH and copper piping, and after 35+ years, pinhole leaks developed. We had never had our water treated for low pH because we didn't know it was problematic. The first leak caused over $3,000 in damage. Since we had no way of knowing how extensive the leaking problem was, or where other leaks might (or already had) develop(ed), we decided to replace all of the piping.
We did consider PEX, but (and this will probably sound like a copout) the repipe project was something my husband was handling, and for reasons I can't recall at the moment, the decision was made to go with CPVC.