The alluminized steel factory pipes are friggin heavy. Corsa and Borla are both crafted from T-304 stainless steel which is the highest grade used in exhaust parts. Many other after market manufacturers (Magnaflow, Flowmaster SOLO use T-409 SS which is certainly an upgrade over alluminized steel but its not the same quality as 304.
I just think Corsa's tips look better and they just flat out sound better. They sound even more amazing with long tube headers.
As an aside, for the V6 you can't beat the mirror polished T-304 ARK DT-S.