The difference between the two.
Copper freezes and breaks...always.
Pex returns to its original state after it freezes...no breaks.
Copper has many joints.
Pex has a joint at the fixture and the manifold.
I'm with you, old school. But since I have been using pex...I will only use copper for returns...to the scrap yard for money.
Don't confuse pex with the older cpvc or crimp on fittings of old. The new stuff cannot be beat.
It was tough for me to accept to.
And I'm an instructor for home inspectors....