Spoiler: It's louder.
Aftermarket exhausts are tricky things. OEM manufacturers spend huge amounts of time and money on getting the sound of the car just the way they want it, while simultaneously maintaining the correct balance of performance and noise levels. For aftermarket companies, improving on this can be difficult. Still, some people are not satisfied with how their cars sound, and here we have an after market option for the F10 M5, the iPE Innotech F1 exhaust.
What's interesting is that the turbo noise is almost completely inaudible except when they're slowing down. Not often you hear that kind of thing.