Compressed Air Piping

Which is better or which do you prefer and WHY? Getting ready to hookup my new to me 5hp 60gal two-stage compressor and I want to run a pipe from front to back of the garage with a couple drops. PVC is out. That is a bomb waiting to happen. So I can use hard copper, iron pipe, or maybe that blue composite stuff Eastwood and others sell. I can go about anywhere and get parts for the copper/iron but not so much the composite. Cost is a factor but I think it is almost a wash between iron and copper? I haven't compared to the kits Eastwood sells.