Here are the results of Sport Auto's comparison test among the M5 F10, Panamera Turbo S, and E63 AMG Performance Package. The M5 doesn't come out on top in the raw number categories, but still gets the nod from Sport Auto for its handling and overall dynamic package.
1st place: BMW M5 - 620 hp on the dyno (claimed: 560)
Tires: Michelin Pilot Supersport
Weight: 1963 kg (4,327 lb)
0-100 km/h (62 mph): 4.3 s
0-200 km/h (124 mph): 13.0 s
Flexibility (80-120 km/h) (50-75 mph) in 5th/6th gear: 4.5 s/5.6 s
Flexibility (80-180 km/h) (50-75 mph) in 5th/6th gear: 12.2 s/15.3 s
18 m slalom: 66.3 km/h
Braking (100-0 km/h) (62-0 mph), warm: 37.5 m
Braking (200-0 km/h) (124-0 mph), warm: 150.0 m
Laptime (Kleiner Kurs Hockenheim): 1:13.6 min
2nd place: Porsche Panamera Turbo S - 555 hp on the dyno (claimed: 550)
Tires: Michelin Pilot Supersport N0
Weight: 2024 kg (4,462 lb)
0-100 km/h (62 mph): 3.7 s
0-200 km/h (124 mph): 12.4 s
Flexibility (80-120 km/h) (50-75 mph) in 5th/6th gear: 4.6 s/7.0 s
Flexibility (80-180 km/h) (50-75 mph) in 5th/6th gear: 11.9 s/16.8 s
18 m slalom: 65.0 km/h
Braking (100-0 km/h) (62-0 mph), warm: 34.9 m
Braking (200-0 km/h) (124-0 mph), warm: 144.2 m
Laptime (Kleiner Kurs Hockenheim): 1:12.1 min
3nd place: Mercedes-Benz E63 AMG PP - 610 hp on the dyno (claimed: 557)
Tires: Continental Sport Contact 5P
Weight: 1941 kg (4,279 lb)
0-100 km/h (62 mph): 4.4 s
0-200 km/h (124 mph): 13.2 s
Flexibility (80-120 km/h) (50-75 mph) in 5th/6th gear: 4.5 s/6.4 s
Flexibility (80-180 km/h) (50-75 mph) in 5th/6th gear: 12.0 s/16.2 s
18 m slalom: 64.9 km/h
Braking (100-0 km/h) (62-0 mph), warm: 37.5 m
Braking (200-0 km/h) (124-0 mph), warm: 151.8 m
Laptime (Kleiner Kurs Hockenheim): 1:14.6 min