Here's a little info from Mercedes.

Check out the stats on the 5.5 liter V12 Bi-turbo:

Engine: 5.5L 36-valve biturbo V-12 engine
Net Power: 510 hp @ 5,000 rpm
Net Torque: 612 lb-ft @ 1,800 - 3,500 rpm

Here's the 5.5 liter supercharged V8:

Engine: AMG-built supercharged 5.5L 24-valve V-8 engine
Net Power: 510 hp @ 6,100 rpm
Net Torque: 531 lb-ft @ 2,600 - 4,000 rpm

They're both 3 valve engines with the same displacement. Both engines run the same amount of boost. The V-12 is a regular production Mercedes engine. The V-8 is a motor that has been heavily massaged by AMG. Notice that the horsepower is the same but the V-12 is kicking AMG's butt in the torque department. The supercharged motor has a torque plateau that lasts 1400 rpm. The turbo motor has a torque plateau that lasts 1700 rpm at a much higher level. It starts earlier too.
Gimme the turbo motor!

The lesson here? Don't mess with a 2003 or newer Mercedes with 600 on the trunk lid or V12 on the side.
If it says V-12 Bi-turbo on the fender or 65 on the deck lid, change lanes and give way in the most courteous manner possible. You're about to get eaten for lunch.

Engine: AMG-built twin-turbocharged 6.0L SOHC 36-valve V-12 engine
Net Power: 604 hp @ 4,800 rpm
Net Torque: 738 lb-ft @ 2,000 - 4,000 rpm

Even the mighty SLR McLaren can't touch the V-12 despite it's HEAVILY massaged supercharged V8.

Engine: AMG-built supercharged 5,439-cc 24-valve 90° V-8 engine
Net Power: 617 hp @ 6,500 rpm
Net Torque: 575 lb-ft @ 3,250 - 5,000 rpm

Maybe more people will now understand why my little black Plymouth is turbocharged and not supercharged.