Regular steel is good, and will last a long time if you don't drive in salt.
Personally I like stainless lines for my trucks. I feel if I am going to spend the time to make the lines and make them look good I should have a more permanent material. I view steel lines as replaceable as a regular maintenance item when the time comes. I view stainless lines as more or less permanent, a lasting solution.
It is difficult to flare. For a little while you can get by with a good quality, but not a cheap, flare tool. If you make lots of lines then a top quality flare tool is a must, but plan to spend some money...
Another brake line option is
http://store.fedhillusa.com/cuniferbrakeandhydline.aspxA copper nickel alloy DOT approved brake line.
I have used it for two short lines on my truck, and I can see that I will be using it more in the future. Very easy to work with, and just as long lasting as stainless, possibly better all around than stainless.
This is one thread about 45 degree double flare tools for stainless
https://www.stovebolt.com/ubbthreads/ubbthreads.php/ubb/showflat/Number/404800#Post404800Grigg