I have driven both so I think my opinion is valid on the subject before I start =) The m5 is very smooth and an amazing vehicle but it's not nearly as fast as the viper . If the driver is very good in the M5 and the viper driver doesn't know what he's doing then he could probably win . The viper weighs much less has more horsepower and higher rear end on it so it's not hard to figure out why . The M5 I drove was a 2000 owned by a friend from church and the Viper is a 98 GTS which has a chip but I have driven it prior to the chip and the chip didn't really do much . I however if I had to pick one of them would take the M5 as it's more civilized for regular driving . -Jarrette