Can anyone tell me why there is a difference in the information provided about the same model of car from Autotrader and Parkers, and which one is accurate?

Take for instance a 2010 BMW 335D M Sport 4dr Auto.

Links to the information on the two websites:

http://www.autotrader.co.uk/classifi...port?logcode=p

http://www.parkers.co.uk/cars/review...on-2005/41356/

The technical information about the car (power, torque, 0-60, MPG, tax band etc) differs between the two sites. Why? And which one is accurate?

Any thoughts appreciated.

Cheers.