I was going to go with copper but decided after much research to try out the RapidAir 3/4 air line system. Cost me a bit more but I also went overkill with the drops and amount of line I ran requiring two kits and extra fittings. I am SUPER happy with the results. It took a bit of time to straighten the hose (did it by hand) as I am very picky and wanted it as straight as possible. I ran 8 drops in my shop. One for the front outside on a shutoff, one to my welding bench, and 2 on each wall without the garage door. This way I don't have to drag a long hose around my cars. I ran one outside so I could run air lines outside with out having to open the garage door. It also gives me the option to place a compressor outside and feed the shop from outside with clean air in case I want to do painting and shut off valve at inside compressor to isolate it. Had it all plumbed in 2 evenings after work. Just make sure you tighten all the fittings properly or you'll get a nice surprise when one pops and it sounds like a gunshot. (Entirely my fault...missed tightening one fitting). Piece of advise if you do go with this system is to throttle your compressor down to 30-50psi and check for leaks with soapy water before running it up to full pressure. Not a bad idea with any system you install.
Excuse the mess in the pictures. This was during garage construction before tools and stuff got organized.