Depends 100% on the grade of stainless, and the thickness of the tubing.
For instance, I would go for a 16ga mild/ceramic header VS an 18ga 409 SS.
304L is ideal if you can afford it, especially if it's 16ga. The higher grade stainless has a much higher oxidizing/carbide temp compared to low grade stainless and mild steel. IE, if built properly, IT WILL last longer.
I've been looking at 3 on Speed Daddy headers.
Stainless steel $125
SS w/ Metallic Paint for Extra Heat and Wearing Resistance $137 And Ceramic Coated & Mild Steel Material $120