copper vs pvc compressor lines?

There is no way I'd use plastic for high pressure air. Our shop used iron pipe. We had a 4 inch manifold pipe across the back of the shop that was slanted from the right. At the low end of the pipe was a drain valve. All of the connections tee-d off the top of the manifold. From there flexible air lines would run to "pigs" which held about a gallon of air and had from 4 to 8 quick connects on them. The paint booth ran a dedicated iron pipe line from the air tank on the compressor with a big drier on it. There were several quick connects in the booth. Guys running motors (e.g. buffers, drills, & saws) could run a line oiler if they saw fit.

The system was supplied by a gigantic Ingersoll Rand 350 cfm compressor running a max pressure of 120 psi. The 100 gallon compressor air tank and the manifold pipe were drained several times during the week. It was usually done at lunch time because it was possible to drain and re-fill the system in about an hour.

In the 3½ years I was with this company the only system failure was one circuit breaker on the compressor motor went out. There were no air line problems ever.