Last time I replaced brake lines I bought steel tube and formed the lines myself.
If you are not comfortable doing that, or don't have the needed time (it didn't take that much) a preformed set could be your answer.
As for stainless over regular steel, if you are forming them yourself the stainless is much harder to get right so I'd stay away from it. But stainless will look nicer longer and probably last longer too, though either is likely to give more then 25 years service.
Its not the cheapest most DIY approach, but I see no reason not to do it if you like the idea.
