Had the chance to drive a M5 back to back with my car. According to official figures, the M5 is quicker than the 996, specially form 100Kph above, but it really doesn't feel like it. You can barely hear the engine from inside the car, although from outside, this V8 has a wonderful growl. Everything is very smooth on the M5 , while on the 996 you can hear and feel every little stone on the road.
Overall I like the M5 because it has a great build quality, lots of space and by switching off the traction control, you can have almost< have the same fun you have in a Porsche, but the road feeling is named Porsche, it's a more driver car than the M5. Best thing is to have both in garage, the Porsche for fun, and the BMW for everyday use, although nowadays there are better options than the M5

J.Seven