Never thought about copper... I did stainless 1/2 hard lines... all An fittings/.. only plastic line I have is 1/8 running to my gauges.. No leaks.. Solid and reliable.. No computer stuff either.. parker valves that are easily servicable.. no sensors, senders, or any extra fittings required.. and I can buy seal kits for the valves at our local parker store.. and you can get to everything.. even if it is sitting on the ground.. I'm with all those guys.. plastic lines are no bueno on a driver. everything through grommets etc...
I am going to make some covers for the valves.. as we get alot of snow..
Is there some advantage to copper over stainless? This stuff is easy to bend. but you gotta buy a good bender...