Not sure if this has been posted before, but it may help when making comparisons:-
http://www.track-challenge.com/main_e.asp
Note the times are given for both Hockenheim and Nurburgring, and the Porker S is a 1999 vintage (252PS)..
Obviously the most unbiased way is as per Dash (and others input) - same driver, same track, two cars..
Plenty of other nice data in there for the anoracks amongst us