I like the copper better.. You can use 1/2in and its not that hard to bend. (like everyone else said) And you can get it almost anywhere.. Back when I bought a 50ft roll, it wasn't but $30. NOt sure how much it is now, but then it was really cheap. I also worked for a A/C company for about 3-4 years and got all the copper I wanted.. So I'm set for awhile..
I originally ran all 1/2 stainless and got swagelock fitting on ebay. What a pain in the ass to run but damn it looks good. Now i got to bend some more because of the new backhalf.