I have 3/4" black pipe in my shop at the farm. Just installed 3/4" pipe in the shop at the house. The cost versus alternatives just worked for me. First setup in the farm shop was PVC. Had a PVC fitting detonate one day. like a shotgun going off. Immediately replaced with pipe. Drip legs at every outlet, drain regularly. Ran my CNC plasma cutter in high Central Texas heat and humidity. dumped a lot of water, but pipe is fine and never had any issues with excessive water. Painting, drain everything, purge water separators, add a good water filter at the outlet your air will come from, and a disposable filter at the gun. knock on wood, no water issues, but I don't paint everyday for a living.
My fear with some of the specialty air supply companies and lines, finding fitting for expansion, changes, or repairs may be tough if the company goes out of business. Its why I now have a mostly defunct CNC plasma table. Availability of repair parts is now an important part of my consideration when buying stuff. Stuff will break, gotta get parts.
