Looking at 997 and 996's. The seats in the 997 look to have worn far worse than the 996. Is that a reflection of a lower quality in the 997 or that the owners of 997 have taken less care.
My experience is only limited to 1 example of each (986 vs 987) but I find that the 987 interior and the seats in particular wear better, but then again it might be down to the the previous owner's care (or light weight!) so not necessarily conclusive...
Ive had 2 986/996 cars, and two 987/997 cars. All the seats were in excellent condition but I wouldn't of bought them if they had been worn, I think a lot depends on the size of driver and types of journeys the car is used for.