Interesting question.......
ex tubing is sometimes aluminized to prevent rust. Fence pipe is galvanized to prevent rust. When
I make an exhaust pipe, I spray galvanize it when my welds are done. I have been using the aluminized pipe. Do you have a non-collapsable tubing bender? What is the price difference in the pipes?

Nothing says the pipe must be a solid piece anyway and bends can get complicated on a long piece. Pretty often I make the system from stock segments, including bends and then use street legal clamps. This allows flexibility, as all ex-pipes want to move.

Welding a solid pipe all the way back encourages breaking as the pipe wants to flex under normal driving and I prefer flexibility instead of broken pipes. Working with segments also allows quicker replacement of a bent section without having to redo the whole pipe. Unclamp and reclamp is faster than saw it out and reweld.

What kind of car are you building it for?-Bob