why do people pay extra for brands?It's just a pipe. Doesn't make any difference except for brand name. Design and all that doesn't make any performance difference
Quality of the material, types of bend (mandrel bend), quality of welding are things that I will look at when considering aftermarket pipe mods which will directly affect the flow. If you are not particular, just ask a shop to punch thru the factory cat, great savings from buying new or used ones.