I can see differences in quality coming up with press, depending on thickness of metal, metal type, force exerted by machine, etc. But mandrel is mandrel.

You can't vary an exhaust that much, unless you decided to drop it below the body and just go straight all the way out. SSA and MBRP to my knowledge follow the same route as the stock system. Greddy 3" mandrel catbacks for my GSX follow the same path as the stocker. Most aftermarket exhausts do. Apexi seems to be the exception with the Tib.