Here is the deal. A ceramic coated shelf header is always made of mild steel. Companies like DC mig weld their mild steel headers and they are usually not welded that well (poor penetration) and that is why they crack. If you take a nice mild steel header and tig weld it or do really good mig welding it will be no more likely to crack than a stainless. Stainless is almost always tig welded for a header. Also never heat wrap anything made of mild steel because it will surely rust fast.

 

The properties of different grades of steel in this case stainless vs mild will most definitely have an affect on sound, just as aluminum or CF pipes would have a different sound. Even after the pipes warm up the sound changes. Maybe it is more noticeable on a 10 cylinder dunno, but without doubt the type of material results in a sound difference.

Whether it is better, worse or barely noticeable is up to the individual.