SportAuto recorded the same lap time (with a BMW M3 3.2, I think) on old and new layout of Hockenheim Short (change around 1997/1998?). General impression is however that the old layout was a bit faster, maybe by half a second or so.
Resurfacing, temperature, tyre (type, mileage, pressure) and especially driver can always lead to huge differences in lap time. Only a direct comparison of cars by a high profile driver is really informative.
The 'masterbike' motorbike track tests with several pro racing riders and about a dozen bikes show how differently the bikes suit the individual riders - and how much a good journalist rider looses and then an average one...