This is definitely the type of information I wanted to see. It is very much like 3d printing: you have materials like brass, stainless steel, copper, even titanium for heatblocks. Most are using brass (probably cost), and some people go right into the copper for its high conductivity, when the plastic being moved through is just a huge insulator - so the real difference is the length of the contact time.
I had never tried to calculate numbers for 3d printing, so I am glad you did it for this. I won't feel the difference looking at SS vs copper. I am leaning towards the copper because it has the fittings right on it - although I can buy compression fittings for stainless that will do the same job (there is a model at the local homebrew shop that is 50' long for roughly same price).