http://www.teknikensvarld.com drove the M5 vs. E55 AMG T.
I'm not gonna go through translating everything, but to my surprise the winner is the E55 AMG.
BMW M5 E60
4 stars in Euro NCAP
0 - 200 km/h 13.73 sec.
402m 12.68 192,4 sec. (very nice trap speed!)
Mercedes Benz E55 AMG Touring
5 stars in Euro NCAP
0 - 200 km/h 14.33 sec.
402m 12.78 188,4 sec.
Please note that this test seems to have been on a dry air strip on winter tires.
Worth noting is that the times on the quarter mile are almost identical, even though the E55 is heavier, has less power and a 5-geared auto.
Up to 70 km/h the AMG is faster.
I would chose the M5 over the E55 (not for looks ), but I think BMW made a huge mistake by having "only" 400 hp as default and then having to use the menues to get the settings I want. (almost 300 to chose from)
Yes, I know there is the M button but if you want to go from there adjusting something? I want to drive, not play a video game.