Sure copper can split, like anything can, but you're talking extreme pressures. 110 psi is nowhere near those pressures. Burst pressure is over 4700 psi, with a working pressure of at least 350(ish) to 1400(ish) depending on the type. Heck the stuff at home depot (L type) is rated for 1002 psi). What compressor do you use that can put that out? Only time I've seen copper split is from freezing in the winter (MinneSnowtan here), and that's obviously not catastrophic, it's just splits quietly and makes a mess when it thaws. Ask me how I know. :)
On the other hand, iron pipe, as you pointed out, rusts, and can push that rust into anything attached to it. You've take great precaution against that which is good, but that's an upside to copper, that doesn't happen. As that iron pipe rusts, it weakens. Again, a win for copper, no rust, ever.
Further, the operation working pressure of the rapid air system is only 200. So, Copper is way safer than the hybrids for now. Especially seeing how it's just aluminum wrapped in plastic. Now, if you're talking about "PEX", the good thing I like is it will "bubble" before it bursts, supposedly, but I can't imagine the time between bubble and burst is very long. At least a bursts might be like a balloon and lose kinetic energy faster than a chunk of iron or pvc, or even copper of you have that kind of pressure, flying across the room.
I'd hate to be around a system that can burst a copper line from air that is used for automotive work. There is something seriously jacked up about that system....
If I am wrong, I really would like to understand where the opinion on copper comes from. I learn new things all the time so please don't take this as some sort of grand challenge. I'd honestly like to know since I'm in the planning stages for mine and was going straight for copper. My compressor us an older 80 gallon IR 5hp unit.
