Practicality wise(heat, ease of fitment, cost) ceramic coated mild steel headers would be the best option.
Any reason for going stainless? If not polished, they will go a very rusty brown colour anyway once they are heat cycled enough. And if they are polished, you will have to fit them with cotton gloves making sure there are no contaminents on the surface as once hot those surface contaminents will be etched into the stainless. I just loved the look of polished stainless headers.
Above web link should be:
http://www.vpw.com.au/
Most people would guess that anyway.