well corsa exhasut is... according to thier website...
100% 304L stainless steel construction with mandrel-bends
304 series stainless has a high chrome content, and can be polished nice to a brillant shine... but is a softer metal due to the chrome content
430 series stainless cannot be polished, but it alot stronger, as it has a high carbon content, it will get a surfance corrosion, but will NEVER rust.
So, the 304 may look nice and shiny, but if you hit a rock, it will dent, and in general, you do not see the exhaust other then the tip unless you are giving your truck an oil change...
I will keep my stronger exhaust system, and the extra $300 I saved going magnaflow....
Grey
Edit:
If you want to check and see what kind of stainless you have... (roughly)
304 stainless is non-magnetic, and is a decorative type material (similar to the tip on the magnaflow or the entire corsa system
430 stainless is slightly magnetic, because of the higher carbon content over the 304. And it is a stiffer more durable material that is less malable.