I think these are the only internally X-pipe mufflers. I doubt anyone has used both but if you have experience with either I would appreciate it. I would use one of these where the rear cats are with a BORLA Pro XS out back. With these 2 mufflers I doubt flow to be restricted much and the car should retain it's quiet stature I like, it's an SLK32 AMG. The BORLA's do NOT drone so that issue is resolved. FYI the Hookers do not drone either, all others do as far as I know and have tried many. What I am really interested in would be how much of an "X Factor" each muffler may have, thee larger cross section for evening the odd exhaust pulses the better. Thanks!