all steel rust... including stainless steel only that stainless steel will rust in a very very long time .. depending on grades of stainless steel use, it typically will start only rust from 5 years onward(greatly depending on the environment) , and good quality stainless can last you about 15-20 years easily. sound great right.. but too bad, in exhaust it does not last that long... hahaa...
for piping you mention, so call white piping is actually a very very general naming...
in traditional exhaust piping, white piping should be refer to aluminized piping, which means a type of metal which hot dip into aluminium silica alloy... this is the only material accepted world wide for exhaust nowdays..
how ever in malaysia, white piping can be "cheated" to consumer eye because the pipe is white and not black, the other white it can be cold rolled form pipe or GI pipe which is zinc coated commonly.... this type of pipe sometime easily pass off as aluminized piping especially for people who don know much about metal.....
black piping, is just normal hot rolled metal,... is actually thickest among all... but the easiest to corrode.. if the black pipe last you one year.. the cold rolled pipe will last you 1.5 year and aluminized easily 2.5-3 times the lifespan..... therefore the cost is different... well of course the stainless easily last 10x hahaha....
however there is con as well... stainless steel is usually thinner gauge and prone to crack due to heat...because of it thermal property... and malaysia hari hari hujan ma... so hot cold hot cold splash splash splash... crack lo.....
black pipe tend to give less problem, because... the pipe it self is already porous... so when the exhaust is heated.. it actually breathing through the pipe and there fore it dont crack that easy.... but as for stainless steel.. it very pack and therefore the suddent hot cold make it crack much easier than aluminized does...
regard the sound is sweeter... well.. that is something very personal for some people... but in general... the sound quality is affect greatly by the pipe thickness...
the sound travel through pipe and the quantum is determine by how thick the pipe is, the thicker the pipe is, it take longer time , more energy to bounce behind, which will create a lower, mellower , more bassy sound...
if the pipe is thin, the sound bounce out will be in higher pitch and more crispy...
so the thicker aluminized pipe or thinner stainless pipe generally create little different behaviour in sound for sure....
interesting to see people are so interested in the piping now... i wonder when Malaysian will start explore sound behavior in exhaust system ... i mean beside the straight flow or s flow... hahhaaa.....